MiniPuck Model ST132-06x0 Two-Wire TC/mV Transmitter
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Acromag, Inc. Tel: 248-295-0880 Email:
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This section of the manual will walk you through the reconfiguration process
step-by-step. But before you attempt to reconfigure or recalibrate this
transmitter, please make the following electrical connections:
Calibration Connections:
1. Connect a precision voltage source or thermocouple calibrator to the
input as required and observe proper polarity.
An accurate input source adjustable over the range desired for zero and
full-scale is required. A thermocouple calibrator may also be used. The
input source must be accurate beyond the unit specifications (better
than ±0.1%). A good rule of thumb is that your source accuracy should
be four times better than the rated accuracy you are trying to achieve
with the transmitter. For voltage inputs, use a voltage source with an
output impedance of 100
or less.
In the absence of a thermocouple calibrator, a convenient method of
configuring the TC input would be to use a precision mV source with the
module’s CJC set to OFF. Using this method allows the mV source to
be wired directly to the input T/C terminals using copper wires. The
module’s cold junction compensation is turned off and the mV values
applied to the input are the equivalent thermoelectric voltages that
correspond to the minimum and maximum temperatures of your desired
input range, and specific to each T/C type. Refer to the table of the
following page for a list of thermocouple voltages at specific
temperatures. After setting zero and full-scale in this manner, the CJC
switch should be returned back to the ON position to enable cold
junction compensation.
2. Wire an output current loop to the transmitter as shown in the Electrical
Connections section. You will need to measure the output current
accurately in order to calibrate the unit. You could connect a current
meter in series in this loop to read the loop current directly.
Alternatively, you could simply connect a voltmeter across a series
connected precision load resistor in the loop, then accurately read the
output current as a function of the voltage IR drop produced in this
resistor (recommended). In any case, be sure to power the loop with a
voltage that minimally must be greater than the 12V required by the
transmitter, plus the IR drop of the wiring and terminals, plus the IR drop
in the load. To compute the IR drop, be sure to use a current level that
considers the over-scale current (~24mA). The output load resistance
and meter must be accurate beyond the unit specifications (better than
±0.1%). A good rule of thumb is that your load and meter accuracy
should be four times better than the rated accuracy that you are trying to
achieve with the transmitter.
Loop Power Supply:
Make sure that your power supply voltage level
is at least 12V plus 0.020*load_resistance. Ideally, it should be great
enough to drive the over-range current of ~24mA into your load (i.e.
greater than or equal to 12V+ 0.024*Rload, assuming the line drop is
negligible and the maximum possible over-range current.
Apply power to the transmitter output loop and always power the loop
before connecting to USB. You will not be able to calibrate the unit
without loop power applied.
CONFIGURATION
STEP-BY-STEP
Calibration
Connections
IMPORTANT:
Do not connect
the transmitter to your PC via
USB without also booting the
configuration software.
Connection to USB is intended
as a temporary connection for
the purpose of setup and
reconfiguration only. If you
connect to USB but do not
boot the configuration, the
output DAC will hold its last
programmed value as the
unit’s microcontroller awaits
initialization via the host
running configuration software.