Calibration
The calibration of the SM815 is accomplished by first
setting DIP switch positions to the proper thermocouple
type and input range and then by calibrating the unit using
the span and zero potentiometers.
To calibrate the SM815 follow the procedure below:
1) Select the temperature range and thermocouple type.
NOTE that the top of the range can be from 4 to 64 mV
above the bottom of the range. The bottom of the range
is always 0 mV (or °C) ±25% of the millivolt span.
2) If you are calibrating using an ice bath and millivolt
source, find the millivolt values in a thermocouple table
corresponding to the top and bottom of your temperature
range. For example, for type J, 60 to 200°F, the millivolt
input will be 0.791 to 4.906 mV. If you are calibrating
using a thermocouple calibrator/simulator the above step
is not necessary. This is because the output of the
calibrator is given directly in units of temperature rather
than in millivolts. NOTE that the output of the SM815 is
linear with respect to the millivolt input and does not
correct for the nonlinearity of the thermocouple wire.3)
Reference table 1 and set the DIP switch positions for the
required thermocouple type and input span. Reference
table 3 for voltage inputs.
4) Set the calibration source to the bottom of the input
range and adjust the zero pot for an output of 4 mA.
5) Set the calibration source to the top of the input range
and adjust the span pot for an output of 20 mA.
6) Repeat steps 4 and 5 until the output readings are
exactly 4 and 20 milliamps.
MILLIVOLT SPAN
4 to 8 8 to 16 12 to 24 16 to 32 20 to 40 24 to 48 28 to 56 32 to 64
SWITCH 4 ON OFF ON OFF ON OFF ON OFF
SWITCH 5 ON ON OFF OFF ON ON OFF OFF
SWITCH 6 ON ON ON ON OFF OFF OFF OFF
TEMPERATURE SPAN
°C 80 -150 150-290 220-420 290-600 370-710 420-760
TYPE J
°F 140 -270 270-530 400-790 530-1050 560-1320 790-1390
°C 100-200 200-390 290-580 390-770 480-970 580-1180 670-1370
TYPE K
°F 175-355 355-705 530-1045 705-1385 875-1740 1045-2115
1210-2500
°C 95-175 175-320 250-400
TYPE T
°F 175-320 320-585 460-750
°C 65-125 125-235 180-325 235-440 285-535 325-635 385-735 435-835TYPE E
°F 120-230 230-430 335-615 430-795 525-975 615-1155 705-1330 795-1515
°C 450-800 800-1400 1115-1700
TYPE R
°F 840-1470 1470-2540
2025-3100
°C 480-860 860-1535 1200-1760
TYPE S
°F 875-1565 1565-2785
2190-3210
Table 1. Switch settings for millivolt and temperature spans (see notes)
TYPE J TYPE K TYPE T TYPE E TYPE R TYPE S
SWITCH 1 ON OFF OFF OFF OFF OFF
SWITCH 2 OFF ON ON OFF OFF OFF
SWITCH 3 OFF OFF OFF OFF ON ON
Table 2. Switch settings for thermocouple type selection
SM815 - MV 4-8 mV 8-16mV 12-24mV 16-32mV 20-40mV 24-48mV 28-56mV 32-64mV
SM815 - V1 0.04-0.08V
0.08-0.16V
0.12-0.24V
0.16-0.32V
0.20-0.40V
0.24-0.48V
0.28-0.56V
0.32-0.64V
SM815 - V2 0.4-0.8V 0.8-1.6V 1.2-2.4V 1.6-3.2V 2-4V 2.4-4.8V 2.8-5.6V 3.2-6.4V
SM815 - V3 4-8V 8-16V 12-24V 16-32V 20-40V 24-48V 28-56V 32-64V
Table 3. Input spans for voltage input models
NOTES
1. All input ranges start at 0 millivolts (or 0°C) with an offset adjustment of approximately ±25% of the millivolt span, using the zero
potentiometer.
2. Table 1 lists maximum and minimum spans for each switch setting. For example with switches 4, 5 & 6 in the on position, the input range can
be set from 0 to 4 mV up to 0 to 8 mV using the span pototentiometer.
