DEVAR SM815 User manual

DEVAR Inc.
Instruction Manual
SM815
mV/TC
TRANSMITTER
MANUAL 990626 Rev. A
Distributed
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INSTRUCTION MANUAL
SM815 ISOLATED T/C TRANSMITTER
The SM815 isolated two wire mV/TC transmitter receives
signals from thermocouples or other millivolt sources and
provides a proportional 4 to 20 mA output signal which is
completely isolated from the input. Because the SM815 is a
two-wire device, a single pair of twisted copper wires are all
that is required to provide power to the unit as well as to
carry the output current.
The SM815 is field calibratable, accepting inputs from type J,
K, E, R, S, & T thermocouples, with millivolt spans ranging
from 4 to 64 millivolts. Thermocouple types and ranges are
selected using a 6-position DIP switch and final calibration is
accomplished by means of multiturn zero and span
potentiometers. The zero pot provides an offset adjustment
of ±25% of the span. The SM815 is provided with upscale
thermocouple break indication. Four voltage input models
are also available, accepting inputs ranging from 4 to 64 mV
to 4 to 64 volts.
General Specifications
Power Requirements 8.5 to 35 VDC at Terminal Block
Accuracy 0.1% of millivolt Span
Working Temperature -25°C to +85°C
Storage Temperature -65°C to +125°C
Thermal Zero Shift 0.01% /°C (span > 10 mV)
0.02 % /°C (span < 10 mV)
Common Mode Rejection 115 dB at 60 Hz
3 dB Frequency 3 Hz
Weight 2.5 oz.
Input Specifications
Sensor Thermocouples J, K, T, E, R, S
Voltage Inputs Option -MV (4 to 64 mV)
Option -V1 (0.04 to 0.64 VDC)
Option -V2 (0.4 to 6.4 VDC)
Option -V3 (4 to 64 VDC)
Input Break Indication Upscale
Input Offset Adjustment ±25% of mV Span
Input Source Current 4 nA Typical
Input Resistance > 3 × 10
7
Ω(TC & mV Inputs)
226K (Options V1, V2, & V3)
Output Specifications
Output Range 4 to 20 milliamps
Output Limits 3 to 28 mA, Typical
Max. Load Resistance = (Supply Voltage -8.5V) / 20 mA
Load Effect <0.01% of Span / 300ΩChange
Power Supply Effect <0.002% of Span per Volt
Options
-CHA Aluminum Connection Head
-CHN Nylon Connection Head
-CHAS Snap Top Connection Head
-CHX Explosion Proof Head
-TCSF Spring Loaded Thermocouple
-TCBF Brazed Thermocouple
-W Thermowell (Specify Length)
-M31S 3 Inch Snap Track Mount
-M31D DIN Rail Mount
FIGURE 1 FIELD WIRING
DEVAR Inc.
DEVAR Inc.DEVAR Inc.
DEVAR Inc.
706 Bostwick Ave., Bridgeport, Ct. 06605
Tel [phone] Fax [phone] Manual No. 990626 Rev. A
http://www.devarinc.com
THERMOCOUPLE
OR
MILLIVOLT SOURCE
SZ
-PS
+PS
-IN
+IN
1
2
3
4
5
INPUT
+
PWR
LOAD +
LOAD +
+
+
1.281
0.260 DIA. THRU HOLE
(2) MTG HOLES
0.171 DIA
1 1/8
3/4
1 3/4
6 5 4 3 1 2
ON
OR
POWER
SUPPLY

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.