| Standard Operating Procedure | SOP No. |
| --- | --- |
| Calibration Procedure for Analog Type Pressure Gauge | 6.021 |

**Effective**: 1-5-2005

DCR No.: 04002

Supersedes: 1-5-2005

Revision No.: 0

Revision Date: 1-5-2005

Page No.: **1 of 4**

## 1 Purpose

1.1 The purpose is to provide guidelines for field calibration on all analog type 
pressure gauges.

## 2 Scope

2.1 This procedure shall cover all analog type pressure gauges that will be 
commissioned by Therma’s Calibration Department.

## 3 Reference

3.1 Manufacturer’s manual for the specific instrument.

## 4 Responsibility

4.1 Field calibration technician shall perform calibration as per the following 
procedure.

## 5 Calibration Equipment and Tools

5.1 Pneumatic Calibrator

5.1.1 Pressure Range: 0.0 to 500.0 PSI

5.1.2 Accuracy: ± 0.25%

5.1.3 Recommended: Trans Cat Pressure Calibrator

5.2 Accessories

5.2.1 Small hand tools

5.2.2 Gauge pointer jack set

5.2.3 Pressure unit conversion table

5.2.4 Miscellaneous tubing, fittings and adapters

5.2.5 Manufacturer’s instruction manual

## 6 Procedures

6.1 Calibrate test instrument (e.g. pressure gauge) with pneumatic calibrator

6.1.1 Connect the pressure gauge to the pneumatic calibrator.  Orient 
the gauge under test, as it would be normally installed.

6.1.2 Exercise the pressure gauge under test by slowly running it up to 
full-scale deflection and back to zero.  Repeat this test for three 
times.

6.1.3 Determine the gauge under test major scale divisions to the 
nearest 10% of full scale.  While lightly tapping the gauge under 
test to minimize the effect of hysteresis and dead band.

6.1.4 Set the gauge under test to this value and record the standard 
readings on a calibration report.

6.1.5 Repeat steps 6.1.3 & 6.1.4 using major scale divisions had 50% 
and 90% of full scales.

6.1.6 Slowly bring the indication down to 50% of full scale and note the 
reading.  Reduce the pressure to 20% of full scale, then slowly 
increase the pressure up to 50% of full scale and note reading.  
The difference between these two readings should not exceed the 
manufacturer’s limit for hysteresis.

6.1.7 Set the gauge to indicate zero. Slowly bring the pressure up to full 
scale, noting whether the pointer movement is jerky or uneven at 
any point on the instrument span.

## 6.2 Calibration Adjustments

6.2.1 If the tolerance is not within the manufacturer’s specified 
accuracy, make a zero adjustment.

6.2.2 Adjust the gauge’s zero by turning a screwdriver adjustment on 
the pointer, or by removing the pointer with a jack set and placing 
the pointer back to the correct position.

6.2.3 Make span adjustment using manufacturer’s instructions if 
necessary.

6.2.4 After completion of adjustments, repeat the calibration procedures 
that described in Step 6.1 and record the readings on a pressure 
gauge calibration form, FN 6.021.1.

## 6.3 Fill out calibration date & due date on a calibration sticker and attach the sticker to the external surface of the gauge.

6.4 Record all calibration data on the pressure gauge calibration form, FN 6.021.1.

## 7 Review and Approval

7.1 The field calibration technician shall submit a copy of the pressure gauge 
calibration form, FN 6.021.1 to project manager.

## Document Approval

Robert McCann

Field Calibration

Quality Assurance Manager

12/30

Date

104

1/5/2005

Date