Calibration Verification of Digital Humidity Indicators

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1.0 Purpose 
 
 The purpose of this SOP is to describe the procedure for the single point calibration verification
 of digital humidity indicating devices. 
 
 2.0 Scope 
 
 This procedure is for the calibration verification of digital humidity indicating devices
 including data loggers and fixed humidity controlled devices with a humidity indicator (i.e.
 stability chamber). Some devices may also measure temperature which is not covered in this
 
 SOP. This SOP does not cover the calibration or repair of any humidity measuring device.
 
 3.0 Responsibility 
 
 4.1 Itis the responsibility of QC Laboratory Personnel to follow this procedure.
 
 4.2 It is the responsibility of QC Laboratory Management to ensure the procedure is current
 and is being followed. 
 
 4.0 Definitions 
 
 41 ISO — International Organization for Standardization 
 
 4.2 TEC - International Electrotechnical Commission 
 
 4.3 NIST — National Institute of Standards and Technology 
 
 44 ANSI- American National Standards Institute 
 
 4.5 NCSL —National Conference of Standards Laboratories 
 
 4.6 %RH- Percent Relative Humidity 
 
 4.7 QC- Quality Control 
 
 5.0 References 
 
 
 

[SOP G-203 | Page 2 of 3]

 Standard Operatii ng Procedure S6O-P2 0N3o Re3 v Page 2 of 3
 Calibration Verification of Digital Humidity Indicators 
 
 5.1 G-201-F2, Form, Calibration Certificate 
 
 5.2 G-201,SOP, Calibration Program 
 
 6.0 Procedure 
 
 6.1 Refer to SOP G-201 Calibration Program for calibration schedule and instructions on
 the documentation of the calibration verification. 
 
 6.2 It is recommended that fixed calibration hygrometers are replaced at least every five
 years. Hygrometers that can be calibrated should be verified or calibrated at an external
 calibration lab at least once every five years. 
 
 6.3 If an indicator fails internal calibration verification and the instrument is able to be
 calibrated the unit must be calibrated and recertified by an external laboratory before
 
 returming to service. 
 
 6.3.1 Exception: If the humidity indicator is a component of a larger piece of
 equipment and specific calibration instructions are available, the humidity
 indicator may be adjusted by personnel familiar with and qualified to perform
 the adjustment. 
 
 6.4 Verification Process: 
 
 6.4.1 For use as a reference standard select a NIST traceable hygrometer that has been
 externally calibrated and verified in compliance with ISO/IEC and/or
 ANSI/NCSL requirements. Internally calibrated hygrometers do not qualify as
 reference standards. 
 
 6.4.2 Select a %RH as the reference point that pertains to the instrument being
 
 verified. For example: if the hygrometer is used at a controlled humidity, verify
 at a %RH within the controlled range. 
 
 6.4.3 All instrument information, calibration verification and environmental data
 should be documented on form G-201-F2 Calibration Certificate.
 
 6.4.4 The common specification for verification is +/- 5°C of reference %RH unless
 
 otherwise specified by the needs of the application or recommended by the
 equipment manufacturer. 
 
 6.4.4.1 For instruments such as stability chambers that have a digital readout
 of the humidity, the fixed humidity of the device can be manually
 adjusted to the fixed point setting using a NIST traceable reference. If
 
 the digital display is out of specified limits an offset can be recorded
 
 
 

[SOP G-203 | Page 3 of 3]

 Standard Operating Procedure SOP No Rev 
 G-203 Page 3 of 3 
 Calibration Verification of Digital Humidity Indicators 
 
 on the calibration verification documentation and the indicator labeled
 with the offset adjustment. 
 
 6.4.5 The common verification cycle for hygrometers is 1 year. 
 
 6.4.6 If a hygrometer is removed from service for any reason including failed
 verification, the device in the Calibration Schedule must be lined out with the
 notation “removed from service.” The device is no longer permitted in GMP
 
 work areas. 
 
6.4.7 For devices that pass verification, a calibration sticker will be attached and the

 unit returned to service. 
 6.4.8 Some devices that have humidity read-outs are only for reference and must be
 noted as so. These devices are not to be used to record temperature and a
 
 secondary, traceable temperature reading device must be used for GMP
 activities. 
 
 7.0 Revision History 

| Rev | Date | Description of Changes | CCR # | By |
|-----|----------|------------------------|-------|----|
| 0 | 05/25/10 | Original - - | - | - |
| 1 | 04/01/13 | Changed the SOP format & number Biennial review: Changed SOP format. Rewrote SOP for calibration | 13-248 | B. Johns |
| 2 | 06/26/15 | verifications. Scheduled review: Added information about humidity monitors that . | 15-0580 | B. Johns |
| 3 | 93/26/19 | are for reference purposes | 19-0243 | J. Maignan |