Fluke 9140 9 Test Probe Calibration

9 Test Probe Calibration

For optimum accuracy and stability,allow the calibrator to warm up for 10

minutes after power-up and then allow adequate stabilization timeafter reach -

ing the set-point temperature. After completing operation of the calibrator, al-

low the well to cool by setting the temperature to 100°Cfor one-half hour

before switching the power off.

For information on automating your testing,contact Hart Scientific.

Insert the probe to be calibrated into the well of the dry-well calibrator. The

probe should fit snugly into the calibrator probe sleeveyet should not be so

tight that it cannot be easily removed. Avoidany dirt or grit that may cause the

probe to jam into the sleeve.Best results are obtained with the probe inserted to

the full depth of the well. Once the probe is inserted into the well, allow ade-

quate stabilization time to allow the test probe temperature to settle as de-

scribed above. Once the probe has settled to the temperature of the well, it may

be compared to the calibrator display temperature. The display temperature

should be stable to within 0.1°C degree for best results.

CAUTION: Never introduce any foreign material into the probe hole of

the insert. Fluids etc. can leak into the calibrator causing damage to the

calibrator or binding and damage to your probe.

Comparison calibration involves testing a probe against a similar reference

probe. The advantage to this method is that better accuracycan be achieved

since errors due to dry-well inaccuracy,stem effect, and drift can be reduced.

After inserting the probes to be calibrated, allow sufficient time for the probes

to settle and the temperature of the dry-well to stabilize.

Both the reference probe and the probe under test should be the same size and

construction. Using probes with different lengths, diameters and materials will

have differentstem effects causing an unknown temperature difference. All

dry-wells have horizontal and verticalgradients that change with temperature .

This is an unknown variablewhich can be factored out if probes are the same

type, length, diameter,and material. Probes should be inserted to the same

depth in the well.

The following procedure can be used to calibrate a probe against a reference

while eliminating error due to temperature gradients between wells.

1. Place the reference probe in one well.

9 Test Probe Calibration

Comparison Methods