voltage given by a thermocouple with a multi-meter. This is because the thermocouple acts as a
differential device between the junctions and the connection of a multi-meter creates a junction
at that point as well. The voltage supplied is for the difference of the temperature at the two
different ends of the thermocouple so the output voltage will be for the temperature difference
between the two points, not the absolute temperature at the measurement tip. This makes
knowing the temperature at the connector critical to getting an accurate measurement. The
connection temperature is known as the cold junction temperature and a compensation must be
included for it’s effect. This is very important as the error in the measurement of cold junction
temperature will be directly reflected as an error in the measured temperature from the
thermocouple. The AEM Thermocouple Amplifier has an internal Cold Junction Temperature
sensor to ensure the accuracy of the output.
EXAMPLE: If the tip of a thermocouple is at 750C and the connection device, or cold junction
is at 100C then the output for the thermocouple will reflect 650C. The cold junction temperature
compensation must be added to the measured value to get the proper answer, 750C. The AEM
Thermocouple amplifier performs all necessary compensations for the cold junction temperature
so you don’t have to worry about it.
ANALOG OUTPUTS
All four temperature channels have high accuracy, 0-5V analog outputs. The calibration is:
Temperature (C) = Volts * 200
Temperature (F) = (Volts * 360) + 32
Example: If 1.45 volts were output: The temperature in Degrees C would be 1.45 * 200 = 290C
The temperature in Degrees F would be (1.45 * 360) + 32 = 554F
Volts
Deg C
Deg F
Volts
Deg C
Deg F
Volts
Deg C
Deg F
0.00
0
32 1.70 340
644 3.40 680 1256
0.10
20
68 1.80 360
680 3.50 700 1292
0.20
40
104 1.90 380
716 3.60 720 1328
0.30
60
140 2.00 400
752 3.70 740 1364
0.40
80
176 2.10 420
788 3.80 760 1400
0.50 100 212
2.20 440 824
3.90 780 1436
0.60 120 248
2.30 460 860
4.00 800 1472
0.70 140 284
2.40 480 896
4.10 820 1508
0.80 160 320
2.50 500 932
4.20 840 1544
0.90 180 356
2.60 520 968
4.30 860 1580
1.00 200 392
2.70 540 1004
4.40 880 1616
1.10 220 428
2.80 560 1040
4.50 900 1652
1.20 240 464
2.90 580 1076
4.60 920 1688
1.30 260 500
3.00 600 1112
4.70 940 1724
1.40 280 536
3.10 620 1148
4.80 960 1760
1.50 300 572
3.20 640 1184
4.90 980 1796
1.60 320 608
3.30 660 1220
5.00 1000 1832
STATUS LEDS
Each thermocouple input has a status LED. It will be lit whenever an open condition is
detected. If a thermocouple is plugged in but the LED is still on then the thermocouple has an
open short somewhere in it and must be replaced.
Page 3
