Field Test and Calibration Method for Temperature for the 61-310 and 61-312 DMMs
Most low cost instruments and Multimeters that measure temperature use Thermocouples {TC}.
Thermocouples are an inexpensive method of measuring temperature. TC can range in accuracy from 2%
to as high as 20% depending on the purity of the metals and construction, so the better the accuracy the
higher the cost of the TC. The TCs that come with low cost instruments are normally of low accuracy,
typically 5% or more.
One nice fact is that regardless of the construction of the TC, if it is being used in normal environmental
conditions the error can be compensated for.
One typically overlooked fact is that Water freezes at 32°F or 0°C and boils at 212°F or 100°C with very
little error due to impurities of the water and barometric pressure.
This can provide a typical user an easy to construct calibration standard of suitable accuracy.
Fill one of those plastic thermal glasses that you have with crushed ice and add enough water to create the
consistency of a slushy. At the same time bring a small pan of water to a boil. Remember that pure water
will work best for this experiment.
There are TCs that are constructed to be submerged in water but most TCs that are packaged with low
cost instruments come with a bead style TC which should not be used in liquids. If you have a bead type
TC use something like a freezer bag or high temperature plastic wrap around the TC.
Now all you need to do is make the measurement.
For best accuracy during the measurement, slowly stir each batch of water as you are making the
readings.
Following the steps below, you now have two reference values (the freezing and boiling points of water)
which are 32 and 212 F or 0 and 100 C to allow you to do a two point calibration for each scale. If you
have a calibrator, then you can choose to make more adjustments at different temperatures.
61-310 Temperature Performance Test:
Step
1
2
3
4
5
6
7
Range
Source Reading
ºC
ºC
ºC
ºC
-20
400
750
ºF
ºF 32 ºF
ºF
1382
ºC -10 to 10
0
ºC -31 to –9
ºC 391 to 409
ºC 721 to 779
ºF -23 to 15
-4
12 to 52
ºF 1328 to 1436
ºC Calibration (Adjust VR2)
1. Set the rotary switch to the "ºC " position.
2. Set the output of the calibrator to 0 ºC
3. Connect the calibrator Temperature output to the V/Ω/Temp and COM input terminals
4. Using a small flat-tipped screwdriver, adjust VR2 for a 0 ºC +/- 1ºC (-1 to 1) display
ºF Calibration (Adjust VR3)
1. Set the rotary switch to the "ºF " position.
2. Set the output of the calibrator to 32 ºF
3. Connect the calibrator Temperature output to the V/Temp and Com input
4. Using a small flat-tipped screwdriver adjust VR3 for a 32 ºF +/- 1ºF (31 to 33) display
61-312 Temperature Performance Test:
Step
Range
Source Reading
1
2
3
4
5
6
7
(D) ºC Calibration (Adjust VR3)
5. Set the rotary switch to the "ºC " position.
6. Set the output of the calibrator to 0 ºC
7. Connect the calibrator Temperature output to the V/Ω/Temp and COM input terminals
8. Using a small flat-tipped screwdriver to adjust VR3 for a 0 ºC +/- 1ºC (-1 to 1) display
(E) ºF Calibration (Adjust VR5)
5. Set the rotary switch to the "ºC " position.
6. Set the output of the calibrator to 300 ºC
7. Connect the calibrator Temperature output to the V/Ω/Temp and COM input
8. Using a small flat-tipped screwdriver adjust VR5 for a 300 ºC +/- 1 ºC (299 to 301) display
ºC
ºC
ºC
ºC
ºF
ºF
ºF
ºC -4 to 4
0
ºC -24 to –16
-20
ºC 293 to 307
300
ºC 722 to 778
750
-4
ºF -8 to 0
ºF 27 to 36
32
ºF 1336 to 1428
1382
(F) ºF Calibration (Adjust VR4)
1. Set the rotary switch to the "ºF " position.
2. Set the output of the calibrator to 32 ºF
3. Connect the calibrator Temperature output to the V/Ω/Temp and COM input
4. Using a small flat-tipped screwdriver adjust VR5 for a 32 ºF +/- 1ºF (31 to 33) display
(G) ºF Calibration (Adjust VR6)
1. Set the rotary switch to the "ºF " position.
2. Set the output of the calibrator to 572 ºF
3. Connect the calibrator Temperature output to the V/Ω/Temp and COM input
4. Using a small flat-tipped screwdriver adjust VR6 for a 572 ºF +/- 2ºF (570 to 574) display
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