Fluke 9107 - Manual (Page 58)

11 Calibration Procedure
11.1 Calibration Procedure
Calibration of this instrument should be performed at regularly scheduled inter-
vals by qualified authorized personnel in accordance with your company’s pol-
icy. Following is the recommended procedure for calibrating this instrument.
11.1.1 Calibration Equipment
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 PRT with a length of 230 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
accuracy of the PRT and the readout which used to display the temperature
should be 0.025°C or better.
11.1.2 Calibration
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 involves measuring the error between the instrument and the refer-
ence thermometer at several temperature throughout the range and adjusting the
calibration parameters as necessary to reduce the errors to within acceptable
limits. The stated accuracy of the instrument 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,
140°C, and –25°C and adjust R0, ALPHA, DELTA, and BETA at each point re-
spectively. Follow these steps:
1. If “as found” data is required then first measure the error at various
temperatures throughout the range such as –25, 0, 25, 50, 75, 100, and
140°C. The errors are measured by setting the controller to the desired
temperature, allowing the block to reach the temperature and stabilize,
and reading the actual temperature of the block with the standard ther-
mometer. If the measured errors are all within acceptable limits then no
further action is required and following the remainder of this procedure
is not necessary. If the accuracy needs to be improved continue with
Step 2.
2. Set the set-point to 0°C and allow adequate time for the block to reach
this temperature and stabilize. Adjust the R0 calibration parameter (see
Section 8.11.1.1) to make the block temperature as measured with the
standard thermometer match the set-point. The approximate ratio be-
tween a change in R0 and a change in temperature at 0°C is about 0.4
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11 Calibration Procedure