GE CTR 80 11 Calibration Procedure

11 Calibration Procedure

Calibration of this instrument should be performed at regularlyscheduled inter-

vals by qualified authorized personnel in accordance with your company’spol-

icy.Following is the recommended procedure for calibratin g this instrument.

Calibration requires a standard thermometer that is adequately accurate and fits

properly into one of the reference holes in the block. Recommended equipment

includes a laboratory grade PRTwith a length of 30 to 300 mm (9 to 12 inches)

and a diameter of 4.76 or 6.35 mm (3/16 or 1/4 inches). The combined accu-

racy of the PRTand the readout which used to display the temperature should

be 0.025°C or better.

The accuracy of the instrument over the full range is determined by the values

of the calibration parameters R0, ALPHA, DELTA,and BETA. The calibration

procedure involvesmeasuring the error between the instrument and the refer-

ence thermometer at severaltemperature throughout the range and adjusting the

calibration parameters as necessary to reduce the errors to within acceptable

limits. The stated accuracy of theinstrument can be found in the specification

table in Section 3.1. Because of the way the calibration parameters affect the

temperature the simplest way to proceed is to measure the errors at 0°C, 100°C,

50°C, and –70°C and adjust R0, ALPHA, DELTA,and BETA at each point re-

spectively.Be aware that you must use the appropriate fluid at each tempera-

ture. Follow these steps:

•Set the set-point to 0°C and allow adequate time for the bath to reach this

temperature and stabilize. Adjust the R0 calibration parameter (see Sec-

tion 9.11.2) to make the bath temperature as measured with the standard

thermometer match the set-point. The approximate ratio between a

change in R0 and a change in temperature at 0°C is about 0.4 to 1. For ex-

ample, if the bath temperature is high by 0.1°C at 0°C then decrease R0

by 0.04.

•Set the set-point to 100°C and allow adequate time for the bath to reach

this temperature and stabilize. Adjust the ALPHA calibration parameter

(see Section 9.11.3) to make the bath temperature as measured with the

standard thermometer match the set-point. The approximate ratio between

a change in ALPHA and a change in temperature at 100°C is about

0.00004 to 1. For example, if the bath temperature is high by 0.1°C at

100°C then decrease ALPHA by 0.000004.

11Calibration Procedure