1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 1 Of 19
Standard Operating Procedure
Humidity & Temperature Indicator Calibration & PM
T Th hi is s D Do oc cu um me en nt t m ma ay y n no ot t b be e r re ep pr ro od du uc ce ed d w wh ho ol ll ly y o or r i in n p pa ar rt t w wi it th ho ou ut t t th he e e ex xp pr re es ss se ed d
W Wr ri it tt te en n P Pe er rm mi is ss si io on n o of f
T Tr re es sc ca al l, , I In nc c. .
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 2 Of 19
Table of Contents
1.0 Purpose ............................................................................................................................................. 3
2.0 Scope ................................................................................................................................................. 3
3.0 Records ............................................................................................................................................. 4
4.0 Responsibility .................................................................................................................................... 4
5.0 Definitions and Acronyms ................................................................................................................. 5
6.0 Reference Material ........................................................................................................................... 8
7.0 Environmental Requirements ........................................................................................................... 8
8.0 Calibration Frequency ....................................................................................................................... 8
9.0 General Safety Issues ........................................................................................................................ 9
10.0 Materials and Test Equipment ........................................................................................................ 10
11.0 Preventive Maintenance ................................................................................................................. 13
12.0 Calibration / Verification Test Methods ......................................................................................... 13
13.0 ‘As Found’ Condition Determination: ............................................................................................. 17
14.0 Adjustments .................................................................................................................................... 18
15.0 ‘As left’ Condition determination: .................................................................................................. 18
16.0 Completion / Data Submittal: ......................................................................................................... 18
17.0 End of Procedure ............................................................................................................................ 18
18.0 Revision History .............................................................................................................................. 19
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 3 Of 19
Humidity & Temperature Indicator Calibration & PM
1.0 Purpose
1.1 The purpose of this Standard Operating Procedure is to standardize the Trescal, Inc., (the Company)
processes used by technicians to perform calibration verifications of Humidity & Temperature Indicator
Instruments. The sole exception is whenever a client specifically requests an exemption to this policy.
2.0 Scope
2.1 This Standard Operating Procedure applies to all Company Field Calibration & Metrology Laboratory
measurement practices and activities that involve comparison measurements between a Humidity
Standard and a Unit-Under-Test Humidity & Temperature Indicator or Water Activity Indicator. This
procedure will provide the general guidelines necessary for the technician to perform these processes
with company owned test equipment.
Figure 2-1, Typical RH&T Hand-held Meter Figure 2-2,RH&T Transmitter
2.2 Limitations
2.2.1 This procedure provides basic guidelines for comparison measurement verification at ambient
environmental conditions, excluding specific adjustment practices which may be performed if
the UUT is found out-of-specification.
2.2.2 Calibration at set points other than local ambient conditions are only possible if the UUT sensor
can be dismounted, and placed within an appropriate Environmental Test Chamber (for either
Temperature or Humidity).
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 4 Of 19
3.0 Records
3.1 Records initiated by implementing this procedure will be considered Quality System Records in their
final approved form, and maintained as such.
4.0 Responsibility
4.1 Quality Assurance:
The Quality Assurance Group is responsible for establishing and maintaining standards of
Company calibration methods, practices and processes (This procedure).
4.2 The Client is responsible for the following:
4.2.1 To designate a site contact(s) for Trescal, Inc. The site contact is responsible for all
communications (verbal and written) between the Trescal, Inc and the client. This includes, but
is not limited to scheduling of all required work, resolution of conflicts, and completion/review
of all necessary paperwork.
4.2.2 To ensure that all client site safety and other required contractor procedures are disclosed to
Trescal, Inc. and that all service personnel assigned to the site have received formal training on
those procedures.
4.2.3 To ensure a safe physical operating environment for all service personnel.
4.2.4 When applicable, to provide operator assistance for equipment of devices that requires
calibration.
4.2.5 To provide all standards and equipment as defined in the project service proposal/agreement.
4.2.6 To provide all necessary documentation (i.e. – manuals, SOPs, etc) to complete all proposed
services.
4.2.7 To retain all original completed documentation by Trescal, Inc. via internal storage procedures.
4.3 Trescal, Inc. is responsible for the following:
4.3.1 To provide qualified service personnel to perform all tasks defined in this procedure. Personnel
qualifications may be based upon formal and/or on-the-job training.
4.3.2 To provide all necessary documentation to the client in a timely manner and compliant with
client requirements.
4.3.3 To provide all standards and equipment as defined in the project service proposal/agreement.
4.4 All Company Personnel
4.4.1 Any Company personnel subject to the scope of the Company Quality Management System,
who perform calibrations of instruments, are responsible for proper implementation of the
practices and processes contained within this procedure.
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 5 Of 19
5.0 Definitions and Acronyms
5.1 Best Measurement Uncertainty [BMU]: Related to the ISO/IEC 17025 Quality Standard definition of the
estimated combined effects of measurement system uncertainties under idealized conditions.
5.2 Cardinal Test Points [RH]: Assigned fixed values of testing that provide a measurement of confidence of
the unit under test condition of calibration. Typically to test a unit across its Range of Interest for
Humidity, an instrument would be tested at three set points; Lower Limit: from 10% to 25%, Mid-scale:
50%, and Upper Limit: from 75% to 90% RH.
5.2.1 A set point from 90% to 100% RH would not normally be selected, because of the danger of
moisture saturating the humidity sensors of the UUT & standard.
5.2.2 A set point from 0 to 5% RH would normally be performed with a Dewpoint Meter, a
measurement covered elsewhere.
5.2.3 Selection of set points in the field are normally limited to Ambient conditions ± available
variable sources (i.e. salt solutions, Hot/Cold Chambers) and are subject to the approval of the
Client requesting 3SP services.
5.2.4 Calibration of Water Activity Indicators in the Metrology Laboratory utilizing the Thunder
Scientific Chamber will be performed with five set points (LL, 0.25, 0.50, 0.75, UL).
5.3 Equilibrium Relative Humidity (ERH): is the value of relative humidity into which a hygroscopic product
can be placed where no net exchange of moisture between the product and the surrounding
environment can take place. It is expressed on a scale of 0…100%. ERH is typically used in the paper and
pharmaceutical industries, but can be applied to almost any product that is sensitive to moisture, or
where the presence of moisture can affect product handling.
5.4 Sorption Isotherm: Water Activity and Moisture Content can be related by a graph called a Sorption
Isotherm (see figure 5-1) so if the user has the ability to measure both parameters, the relationship can
be defined and each parameter derived from the other (interpolation).
Figure 5-1, Sorption Isotherm
In practice, the Sorption Isotherm may be impractical to use, because, not only does the
relationship between aw and moisture content change with temperature of measurement, but
also any variation in the material composition has a modifying effect. This is especially the case
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 6 Of 19
with products of natural origin such as food and paper. The user should therefore decide which
parameter of measurement is best suited to their product and processes. For quality control
purposes moisture content limits are easily converted to Water Activity limits by very simple
comparative tests. Water Activity offers a non-destructive, easy to use measurement in a wide
range of convenient configurations for both laboratory and on-site use.
5.5 Moisture content: when referring to a solid material, is an expression of the percentage of the materials
weight which is water (both in liquid or gaseous phase); usually referred to as ‘percent moisture
content’. This term is widely used in many areas of industry.
5.6 UUT: Abbreviated form of “Unit-Under-Test” (also DUT).
5.7 Water Activity (A W): is the relative humidity which is reached at equilibrium in a sealed container in
which a hygroscopic product has been placed, but expressed on a scale of 0…1, where 0...100 % RH
equals (0.00...1.00 A W). Water Activity measurement is most commonly used in the food industry, where
it is used to determine shelf life and quality.
Water activity defines the active part of a product’s moisture content, or ‘free’ water. It
influences the microbiological, chemical and enzymatic stability of perishable products such as
foods, grain and seeds.
Figure 5-2 Contaminant Growth Thresholds
Figure 5-2 shows typical growth thresholds below which the specified contaminant cannot
replicate, and therefore spoil the product. Control of water activity therefore has a significant
impact on shelf life. For similar reasons, water activity is equally relevant in the pharmaceutical
industry where it also provides useful information regarding properties such as the cohesion of
tablets, agglomeration of powders, and adherence of coatings.
5.8 Relative Humidity: Relative humidity (abbreviated RH) is the ratio of the partial pressure of water
(actual vapor density (g/m )) to the equilibrium vapor pressure of water (saturation vapor density
3
3
(g/m )) at the same temperature.
Relative humidity depends on both temperature and the pressure of the system of interest (nominally
1013 mbar at sea level). Both Rotronic and Vaisala publish an Humidity calculators which allow you to
convert to other moisture units (dewpoint, frostpoint, etc)
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 7 Of 19
Rotronic: http://www.rotronic.com/humidity_measurement-feuchtemessung-
mesure_de_l_humidite/humidity-calculator-feuchterechner-mr
Vaisala (Registration required):
http://www.vaisala.com/en/services/technicalsupport/downloads/humiditycalculator/Pages/default.as
px
Figure 5-3, Graphic - Amount of Water in Air as a function of Temperature
5.9 Hygrometer: A hygrometer is an instrument used for measuring the moisture content in the
atmosphere (not to be confused with hydrometer). Humidity measurement instruments usually rely on
measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical
change in a substance as moisture is absorbed. By calibration and calculation, these measured quantities
can lead to a measurement of humidity. Modern electronic devices use temperature of condensation
(the dew point), or changes in electrical capacitance or resistance to measure humidity differences.
Figure 5-4, functional operation of typical Hygrometer Sensor
5.10 All other terms and definitions that are utilized in this procedure have been deemed as “common
knowledge” and as such are not defined in this section.
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 8 Of 19
6.0 Reference Material
6.1 ANSI/ISO/IEC 17025: current revision: International Standards, General requirements for the
competence of testing and calibration laboratories; November 2017.
6.2 ASTM E104: current revision: ASTM Standard Practice for Maintaining Constant Relative Humidity by
Means of Aqueous Solutions.
6.3 21 CFR Part 11 - Electronic Records; Electronic Signatures, Code of Federal Regulations, Title 21 - Food
and Drugs, Chapter I - Food and Drug administration, Office of the Federal Register, Maryland, USA.
7.0 Environmental Requirements
7.1 In the measurement of humidity it is essential that temperature equilibrium is reached. Even a small
difference in temperature between the UUT and the Standard sensor causes an error. If the Ambient
Temperature is +20 °C and the relative humidity 50 % RH, a difference of ± 1 °C between the measured
UUT and the Standard Sensor causes an error of ± 3 % RH.
7.2 With the same conditions as noted above, but with the humidity at 90 % RH, the corresponding error
increases to ± 5.4 % RH (The error is at its greatest when the sensor is colder or warmer than the
surroundings and the humidity is high).
7.3 A temperature difference of a few degrees can also cause water to condense on the sensor surface. In
an unventilated space evaporation may take hours; good ventilation accelerates evaporation.
7.4 A Humidity sensor starts to function normally as soon as the water has evaporated, however
contaminates in the condensation remains may affect the probe. If the condensed water is highly
contaminated, the life span of the Humidity sensor will be reduced and the calibration curve will change.
7.5 The Temperature of the test environment, should be within 16 °C to 30 °C, and stabilized at least 1.0
hours prior to test, and throughout the measurement process.
7.6 The Ambient Relative Humidity should be maintained within 30% to 75% during the measurement
process.
7.7 The Unit-Under-Test should be free of excessive vibration & air currents.
7.8 The lighting should be of necessary intensity and glare free. Direct sunlight should be avoided.
7.9 The average barometric pressure in the test environment is set nominally at 1013 mBar, and may be
adjustable when measuring moisture content in a pressured vessel.
8.0 Calibration Frequency
8.1 This procedure is to be performed nominally every 3 to 12 months; depending on critically of
measurement, frequency of usage, or whenever changes or repairs have been made that may affect the
accuracy of the UUT measurement.
8.1.1 Critical Humidity probes – 3 months (Process control)
8.1.2 Non-critical Humidity probe – 12 months (General Work space monitor)
8.2 Actual calibration intervals are to be defined & established by the Client.
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 9 Of 19
9.0 General Safety Issues
9.1 The following are general safety issues. Not all may apply to this procedure directly:
9.1.1 Wear the proper safety attire. This may include, but is not limited to: safety glasses, safety
shoes, hard hats, full-face shields, lab coats/aprons, and gloves.
9.1.2 Inspect area for potential hazardous conditions (i.e. – wet floors, exposed electrical wires,
loosely hanging overhead equipment, other personnel working in the area, etc.).
9.1.3 Ensure that UUT Instruments used with bio-hazardous materials have been decontaminated by
the Client properly IAW local protocols, before attempting service.
9.1.4 If Utilizing Saturated Salt Solution, especially Lithium Chloride (CAS 7447-41-8) exercise care in
handling, and avoid ingesting or open sore/eye contact (see SDS).
9.1.5 Be aware of the potential for pinching hazards that exists with the UUT & surrounding
assemblies, and keep hands away from any associated compression/tension assemblies during
testing, as applicable.
9.2 Refer to General Safety Practices: ISO-QSP-2117 for all other safety related issues.
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 10 Of 19
10.0 Materials and Test Equipment
The following materials and equipment may be necessary for the completion of this procedure:
Test Equipment Type Required Parameters for 4 : 1 TAR / TUR
1
0.001 mA Resolution, 4 to 20 milli-Amp Loop, or
0.001 Volt Resolution, 0..10 Volt Input
Process Meter NIST Traceable Standard
or
Process Calibrator UUT milli-Amp ± 0.005 mA ± 0.001 mA Accuracy
or or
UUT Volt ± 0.005 Volt DC ± 0.001 Volt DC Accuracy
Test Equipment Type Required Parameters
± 0.01 °C Resolution
RTD Thermometry System
NIST Traceable Standard
± 0.05 °C Accuracy
Secondary Reference RTD Probe
NIST Traceable Standard
± 0.20 °C Accuracy
Field Industrial Reference RTD Probe
NIST Traceable Standard
Ambient Temperature Test Chamber 10 °C to 40 °C, 0.1°C Stability
Size is determined by specific sensor
Manifold
diameter and spacing requirements.
Field RH Test Chamber 10 % to 90 % RH, ± 1 % RH Accuracy
Field RH Test Standard 10 % to 90 % RH, ± 1 % RH Accuracy
Metrology Laboratory RH Test Standard; i.e. Thunder 10 % to 90 % RH, ± .6 % RH Accuracy
Scientific 2500ST
Metrology Laboratory A W Standard
.10 aw to .90 aw, ± .06 aw Accuracy
Where A W =P/P S , % ERH = 100 x A W
P=Partial Pressure, P S =Saturation Pressure
Saturated Salts in Aqueous Solution: Lithium Chloride (Li-Cl),
Magnesium Chloride (Mg-Cl2), Sodium Chloride (Na-Cl) Reagent Grade, CoA, headspace
Salt Slurry In sealed container, as Humidity Source – temperature compensated
headspace temperature compensated
DI Water, Reagent Grade, as Humidity Source Reagent Grade, CoA
1 Measurement TAR/TUR below 4:1 are to be reported on the Gen•Cal II™ Calibration Report.
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 11 Of 19
10.1 Minimum Use Specifications
Comparison Calibration Test Point Limitations
Method: Single Set Point (1SP) or 3 Set Point (3SP) testing (T/RH)
2
Unit Under Test Typical Test limits [from 10% (LL) to 90% (UL) RH] Typical TUR
3
Reported
Chart-recorder ± 3% RH, tested at Ambient (1SP) or (LL) to 25%, TUR (Field) = 3:1
50%, 75% to (UL) RH (3SP) TUR (Lab) = 4:1
± 2 ° C, tested at Ambient (1SP), or Ambient, TUR (F/L) = 4:1
Ambient + 10 °C, Ambient -10 °C (3SP)
Data-logger ± 2% RH, tested at Ambient (1SP) or (LL) to 25%, TUR (Field) = 2:1
50%, 75% to (UL) RH (3SP) TUR (Lab) = 2:1
± 1 ° C, tested at Ambient (1SP), or Ambient, TUR (Field) = 4:1
Ambient + 10 °C, Ambient -10 °C (3SP) TUR (Lab) = 4:1
Transmitter ± 1% RH, tested at Ambient (1SP) or (LL) to 25%, TUR (Field) = 1:1
50%, 75% to (UL) RH (3SP) TUR (Lab) = 2:1
± .1 ° C, tested at Ambient (1SP), or Ambient, TUR (Field) = 1:1
Ambient + 10 °C, Ambient -10 °C (3SP) TUR (Lab) = 4:1
Indicator ± 1% RH, tested at Ambient (1SP) or (LL) to 25%, TUR (Field) = 1:1
50%, 75% to (UL) RH (3SP) TUR (Lab) = 2:1
± .4 ° C, tested at Ambient (1SP), or Ambient, TUR (Field) = 2:1
Ambient + 10 °C, Ambient -10 °C (3SP) TUR (Lab) = 4:1
Water ± .012 aw, tested at (LL) to .25 A W , .50 A W , .75 A W TUR (Lab) = 4:1
Activity to (UL) .90 A W (5SP) No Field Cal
Meters available
± .3 ° C, tested at Ambient (1SP), or Ambient, TUR (Lab) = 3:1
Ambient + 10 °C, Ambient -10 °C (3SP) No Field Cal
Available
2 LL = Lower Limit, UL = Upper Limit
3 Measurements ≥ ± 4 %RH, ± .4 °C, UUT Accuracy Limits are at least a 4:1 TUR in all cases and TUR need not be reported on Gen•Cal II™ Calibration Report.
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 12 Of 19
10.2 Formulas & Conversions
• Temperature Conversions
TEMPERATURE
To Convert Into Multiply By
°F °C (0.556 x °F) - 17.8 °C
°C °F (1.8 x °C) + 32.0 °F
°C °K (1.0 x °C) + 273.0 °K
• Loop Value Interpolation
To interpolate a value for any process variable in a given milliamp process loop (for RH
Transmitters), the general rules of linear interpolation table apply;
− )( − )
B
X = ( A A B B1 +
2
m
1
−
( A A 1 ) 1
2
X = unknown (Process Variable)
A m = measured amount (mA)
A 1 = lower of the two amounts bracketing the measured amount
A 2 = higher of the two amounts bracketing the measured amount
B 1 = value (from table) for A 1
B 2 = value (from table) for A 2
For Example:
Milliamp Output Process Variable
4.00 mA A 1 0.0 % RH B 1
16.25 mA A m ???? % RH X
20.0 mA A 2 100.0 % RH B 2
If a 4 to 20 milli-Amp is scaled from 0 to 100 %RH, and the loop is reading 16.25 mA, what is
the Process Variable?
X = ( 16 . 25 − 00.4 )(100 − 0 ) + 0
(20 − ) 4
Or
X = ( 16 . 25 − 00.4 )(100 )
( )
16
Therefore
X = 76.6 % RH
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 13 Of 19
11.0 Preventive Maintenance
11.1 Visually inspect the unit and record any damage or wear in the Comments section of the Calibration
Data Form. Repairs may be made, if necessary. Visual inspection should consist of the following items:
11.1.1 Fasteners, screws and bolts
11.1.2 Battery, battery charger and/or power cord
11.1.3 Units housing and internal Ni-Cad battery
11.1.4 Electrical connections and terminals
11.1.5 Sampling hoses and equipment
11.2 The Sensor Filter should be replaced periodically; at least annually for Water Activity meters used on a
daily basis (Not applicable to all models).
11.3 The Sensor screen should be replaced periodically on Humidity Probes, especially if the membrane is
exposed to chemicals, Dust and dirt.
11.4 Inspect the Temperature Sensing Element leads to insure that they have not been damaged during
filter/screen replacement.
11.5 Document any abnormalities or repairs in the comments field of the Calibration Report.
12.0 Calibration / Verification Test Methods
12.1 Humidity Calibration Process:
Place the standard probe near the UUT probe within the same stable ambient environment or
chamber, and allow adequate stability time (30 minutes minimum) after chamber set-up /
recovery period (as applicable) to allow the standard probe to track the UUT probe at the same
Humidity rate (and at the same body temperature). If using a chamber, a manifold can be used
inside the chamber to improve probe response as the humidity gas flows directly over the UUT
and standard. Place both the UUT probe and the standard in the manifold.
12.1.1 Mid-Scale [Ambient] SP2 or Single Set Point SP1:
Place the UUT in the Test Chamber with a Humidity Source capable of maintaining the
Test Chamber Humidity environment at 50% RH (or within ± 1% RH of an ambient
reference value):
12.1.1.1 Allow adequate stability time (nominally 30 minutes) after Test Chamber set-up
recovery period to allow the Standard to track the UUT temperature at the same
rate. [TP120 only: record the time that the measurement was performed as well].
12.1.1.2 Record the UUT Humidity certified value at the same approximate time as the
standard measurement was recorded.
12.1.1.3 If UUT is to be single point verified only, go to step 13.0 otherwise continue.
12.1.2 Lower Limit [Dry] SP1:
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 14 Of 19
Place the UUT in the Test Chamber with a Humidity Source capable of lowering the Test
Chamber Humidity environment to 10% RH or at least 10 % RH below the mid-scale set
point (SP2):
12.1.2.1 Allow adequate stability time (nominally 30 minutes) after Test Chamber set-up
recovery period to allow the Standard to track the UUT temperature at the same
rate.
12.1.2.2 Record the Standard Humidity indication [Dickson™ TP120 only: record the time
that the measurement was performed as well].
12.1.2.3 Record the UUT Humidity certified value at the same approximate time as the
standard measurement was recorded.
12.1.3 Upper Limit [Wet] SP3:
Place the UUT in the Test Chamber with a Humidity Source capable of raising the Test
Chamber Humidity environment to at least 10 % RH above the mid-scale set point (SP2):
12.1.3.1 Allow adequate stability (nominally 30 minutes) after Test Chamber set-up
recovery time to allow the Standard to track the UUT temperature at the same
rate.
12.1.3.2 Record the Standard Humidity indication [Dickson™ TP120 only: record the time
that the measurement was performed as well].
12.1.3.3 Record the UUT Humidity certified value at the same approximate time as the
standard measurement was recorded.
12.2 Temperature Calibration Verification:
12.2.1 Mid-Scale [Ambient] SP2 or single Set Point SP1:
Place the UUT in the Test Chamber with a Thermal Source capable of maintaining the
Test Chamber Temperature environment at 20 °C (or within ± .2 °C of an ambient
reference value):
12.2.1.1 Allow adequate stability time (nominally 30 minutes) after Test Chamber set-up
recovery period to allow the Standard to track the UUT temperature at the same
rate. [Dickson™ TP120 only: record the time that the measurement was performed
as well].
12.2.1.2 Record the UUT temperature indication at the same approximate time interval as
the standard measurement was recorded.
12.2.1.3 If UUT is to be single point verified only, go to step 13.0 otherwise continue.
12.2.2 Lower Limit [Cold] SP1:
Place UUT in a Test Chamber with a Thermal Source capable of lowering the Test
Chamber Temperature environment to at least 10 °C below the mid-scale set point
(SP2), maintained within ± 0.2°C of a reference value:
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 15 Of 19
12.2.2.1 Allow adequate stability time (nominally 30 minutes) after Test Chamber set-up
recovery period to allow the Standard to track the UUT temperature at the same
rate.
12.2.2.2 Record the Standard Temperature indication [Dickson™ TP120 only: record the
time that the measurement was performed as well].
12.2.2.3 Record the UUT Temperature certified value at the same approximate time as the
standard measurement was recorded.
12.2.3 Upper Limit [Hot] SP3:
Place the UUT in Test Chamber with Thermal Source capable of raising the Test
Chamber Temperature environment to at least 10 °C above the mid-scale set point
(SP2), maintained within ± 0.2 °C of a reference value.
12.2.3.1 Allow adequate stability time (nominally 30 minutes) after Test Chamber set-up
recovery period to allow the Standard to track the UUT temperature at the same
rate.
12.2.3.2 Record the Standard Temperature indication [Dickson™ TP120 only: record the
time that the measurement was performed as well].
12.2.3.3 Record the UUT Temperature certified value at the same approximate time as the
standard measurement was recorded.
12.3 Humidity & Temperature Comparison Calibration [Saturated Salt Solutions]:
4
Note: Those Instructions in [brackets] were originally developed for use with Dickson™ Data-
loggers, model TP120, and may be suitable for calibration of similar designed instruments;
compact self-contained Data-loggers with serial PC interface, and 2 channel (Temp/Humidity)
recording capabilities.
The use of saturated salt solutions is strictly optional, and presented here as an alternative
method (The preferred method is with a Variable Humidity Test Chamber).
12.3.1 Additional Reference Material [Dickson™ TP120 only]:
12.3.1.1 Dickson™ TP120 Logger Cal Software, (Version 1.97 or higher) or equivalent
12.3.1.2 Dickson™ TP120 Dicksonware™ Software, (Version 8.0 or higher) or equivalent
12.3.2 Additional Equipment Required [Dickson™ TP120 only]:
12.3.2.1 Data-Acquisition System: Scalable 0.00 to 1.00 Volt / 0 to 100 % RH, data-logged
(un-monitored) or real-time display indicator – multimeter/Process Calibrator
(monitored).
12.3.2.2 WIN98/ME/XP Computer minimum
4 Follow ASTM E 104 – 02: Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions, October 10, 2002 when making salt
solutions.
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 16 Of 19
12.3.3 Additional Expendable Material Required [Dickson™ TP120 only]:
• Distilled Water, Reagent Grade, local source
• Glass Dishes (3), with Lids
• Lithium Chloride in aqueous solution [nominally 12% RH]
• Magnesium Chloride in aqueous solution [nominally 33% RH]
• Sodium Chloride in aqueous solution [nominally 75% RH]
• RS 232 Serial communication Cable [if applicable]
• Dickson™ Serial Download Cable [if applicable]
Table 12-1, Saturated Salts cmu at reference Temperature.
Temperature Lithium Magnesium Sodium
°C Chloride Chloride Chloride
0 11.23 ± 0.54 33.66 ± 0.33 75.51 ± 0.34
5 11.26 ± 0.47 33.60 ± 0.28 75.65 ± 0.27
10 11.29 ± 0.41 33.47 ± 0.24 75.67 ± 0.22
15 11.30 ± 0.35 33.30 ± 0.21 75.61 ± 0.18
20 11.31 ± 0.31 33.07 ± 0.18 75.47 ± 0.14
25 11.30 ± 0.27 32.78 ± 0.16 75.29 ± 0.12
30 11.28 ± 0.24 32.44 ± 0.14 75.09 ± 0.11
35 11.25 ± 0.22 32.05 ± 0.13 74.87 ± 0.12
40 11.21 ± 0.21 31.60 ± 0.13 74.68 ± 0.13
45 11.16 ± 0.21 31.10 ± 0.13 74.52 ± 0.16
50 11.10 ± 0.22 30.54 ± 0.13 74.43 ± 0.19
Reference: Humidity Fixed points of Binary Saturated Aqueous Solutions, Lewis Greenspan, NIST, Journal
of Research Vol. 81A, No. 1, 1977 5
12.3.4 Equipment Set-up [TP120 only] (One or three Set point [SP])
Connect the Humidity & Temperature Standard Humidity signal output(s) to input
channels of the Data Acquisition System or of the real time monitor (comprising the
Standard):
12.3.4.1 Program Data Acquisition system to data log Temperature/Humidity
channels at the same sample rate as the UUT (For example, when testing the
Dickson™ TP120, use Dicksonware™ Software to program the UUT for 30 to 60
seconds intervals, and then activate scan).
12.3.4.2 Connect UUT to PC via Serial Download cable and Place UUT in a stable ambient
environment or chamber.
12.3.4.3 Place the standard probe near the UUT within the same stable ambient
environment or chamber.
5 It should be noted that references dated before 1990 contain data relative to temperature scales other than ITS-90. For best accuracy these data values must be
corrected for the difference between ITS-90 and the temperature scale in question (IPTS-68, IPTS-48).
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 17 Of 19
12.3.5 Activate all data-logging monitors and allow up to 30 minutes for the UUT to stabilize at each set
point.
12.3.6 Repeat steps in 12.3 as necessary for each Temperature & Humidity Setpoint.
12.4 Water Activity Indicator Calibration:
12.4.1 Water Activity Meter Temperature Calibrations are identical with respect to temperature as in
steps 12.2 above.
12.4.2 Water Activity Meter A W Calibration are similar to the Humidity Calibration steps in 12.1 except
as follows;
12.4.2.1 The units of A W are an Equilibrium Relative Humidity (ERH) scale from 0 to 1.00 A W,
which relate to moisture content of a given material at a reference temperature in
a given headspace over time. The measurement cup normally provides that sealed
test volume and ambient thermal stability.
12.4.2.2 The A W scale of 0 to 1.00 is equivalent to the RH scale of 0 to 100% RH at the
temperature reference.
12.4.2.3 Remove the measurement cup to expose the sensor, and place the sensor
assembly within the Humidity chamber.
12.4.2.4 The probe should be thermo stabilized at the desired reference temperature
before taking valid ERH readings (i.e. 20 °C, 25 °C, and 30 °C). 25 °C is the default
value.
12.4.2.5 A tolerance of ± 0.015 A W is equivalent to ± 1.5 % ERH.
12.4.2.6 The Aw probe may need to be programmed to read A W at the desired reference
temperature, for a given sample time. Example at 25.0 °C read X samples/seconds
for 5 minutes, then display A W mean value.
12.4.2.7 The A W Probe Sensor is identical to Capacitive Humidity Sensors in design and
should never be exposed to 1.00 A W!
13.0 ‘As Found’ Condition Determination:
13.1 Compare the noted Certified Value(s) from the ‘As Found’ data to the UUT instrument tolerance limits as
specified.
13.2 If all the Certified Values (C.V.) noted are in tolerance, report ‘as-found data’ as ‘as-left’ and go to final
section 16.0.
13.3 Depending on the As-found condition, the UUT may need to be repaired, optimized or adjusted before
collecting the final ‘as-left data’.
13.4 Refer to ISO-QSP-2010 General Field Service and Calibration Practices.
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 18 Of 19
14.0 Adjustments
14.1 Adjustments are performed per individual OEM Instructions, and are not included within the scope of
this calibration procedure.
15.0 ‘As left’ Condition determination:
15.1 Collect ‘As Left’ C.V. Data as applicable, using the applicable methods of section 12.0:
15.2 Compare the noted C.V. Data from the ‘As Left’ test data taken to the UUT tolerance limits as specified.
15.3 Depending on the As-left condition, the UUT ‘As Left’ data must be entered on the Calibration Report as
applicable.
16.0 Completion / Data Submittal:
16.1 Determine if the UUT Instrument is within specified tolerance (reference, ISO-QSP-2010 General Field
Service and Calibration Practices):
16.2 If UUT Instrument is within tolerance, “As Found” C.V. data may be recorded as “As Left” C.V. data. If
UUT Instrument is not found to be within tolerance, adjust as necessary (reference, ISO-QSP-2010
General Field Service and Calibration Practices).
16.3 If any adjustment has been made, repeat measurement set points per applicable calibration steps in
section 12.0 and record final ‘as-left’ C.V. data once the UUT Instrument has been restored to an in-
tolerance condition.
16.4 Tag and Label UUT Instrument with an appropriate status label as specified in ISO-QSP-2010 General
Field Service and Calibration Practices.
16.5 Complete the calibration data form as specified in ISO-QSP-2010 General Field Service and Calibration
Practices.
16.6 Remove old calibration sticker and replace with the appropriate new sticker (reference, ISO-QSP-2010
General Field Service and Calibration Practices).
16.7 Complete all documentation and review prior to submittal to Client.
16.8 Compile all Calibration Reports in pdf files and submit documentation for review and approval by Client.
17.0 End of Procedure
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.
1565 Bustard Road
Lansdale, PA 19446
Phone: 610-287-3433 Fax: 610-287-0233
Web: trescal.us
Document Type: Standard Operating Procedure Effective Date: 19 Dec 2022
Title: Humidity & Temperature Indicator Calibration & PM
ID: ISO-SOP-3085 Revision: 6.00 Page: 19 Of 19
18.0 Revision History
Rev. Date Description of Change Approvals
No. Signature
0.00 19 Apr 2004 Development of new SOP extracted from M. Salton
GENCAL001,and ISO-CWI-3088 for field Calibration Review/Editor
reference NA
M. Cabanas
Final Approval
NA
1.00 17 Aug 2004 Prepared extracted document for field distribution. M. Cabanas
Review/Editor
See TMS Master File
J. Morwald
Final Approval
See TMS Master File
2.00 28 Nov 2007 Consolidating Humidity Testing Procedures, both CWI & M. Cabanas
SOP into single document, Review/Editor
Replacing; CWI-3014, CWI-3019, CWI-3030, CWI-3031, See TMS Master file
CWI-3032, CWI-3033, CWI-3042 & CWI-3088 and any S. DeSmedt
related Humidity CWI Procedures Final Approval
See TMS Master file
3.00 12 Oct 2011 Updated Document format & Headers, added ‘Water D. Gabel
Activity’ Indicator calibration section, and included Review/Editor
reference to Metrology Laboratory practices to See TMS Master file
harmonize protocol. M. Cabanas
Final Approval
See TMS Master file
4.00 03 Jun 2015 Formatting was updated. GenCal references were L. Myles
updated to GenCal II. Table 2-1 Comparison of Test Review/Editor
Point Limits was moved to section 10.0. Temperature See TMS Master file
requirements were updated in section 7.0. Reagents M. Cabanas
were added to section 10.0. Section 8.0 included more Final Approval
direction on selection of calibration frequency. See TMS Master file
5.00 30 Nov 2018 Update ISO 9001:2015 references A. Hooper
Review/Editor
See TMS Master file
L. Myles
Final Approval
See TMS Master file
6.00 14 Sep 2022 The company name was updated to Trescal and use of Review/Editor Digitally signed by DavidSGabel
a manifold within a chamber was added. Reason: I reviewed this
document
Date: 2022.09.14 13:41:06 -04'00'
Final Approval Digitally signed by Lisa Myles
Date: 2022.09.14 15:35:20
-04'00'
This document when printed from the electronically secured and controlled TMS program is an uncontrolled document. Current revision level
should be verified via TMS prior to use.
© COPYRIGHT 2022-2024, CONFIDENTIAL & PROPRIETARY
TRESCAL, INC.