Model TT231-0600
Two-Wire RTD Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 14 - http://www.acromag.com
- 14 -
http://www.acromag.com
TECHNICAL REFERENCE
OPERATION STEP-BY-STEP
Connections
This section will walk you through
the Connection-Configuration-
Calibration process step-by-step.
But before you attempt to
reconfigure or recalibrate this
transmitter, please make the
following electrical connections
Note: Your input source and output meter must be accurate beyond the unit
specifications, or better than ±0.1%. A good rule of thumb is that your equipment
source accuracy should be four times better than the rated accuracy you are trying
to achieve with this transmitter.
1. Connect Input:
Refer to Sensor Input Connections of page 7 and connect a
precision resistance decade box or RTD calibrator to the input, as required.
Your resistance source must be adjustable over the range desired for zero and
full-scale. A 3-wire or 4-wire sensor connection is recommended, as this will
compensate for sensor lead resistance (this unit will use 3-wire lead
compensation for 4-wire sensors). Be sure to either wire a third lead to the
remote sensor, or install a short copper jump-wire between input terminals 3
& 4 of the transmitter, as this serves as the return path for the excitation
current and must be present for operation.
2. Connect Output/Power:
Refer to Output/Power Connections of pages 7-9 and
wire an output current loop to the transmitter as illustrated. 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
(not recommended). 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 IR voltage 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 9V 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 and alarm limit by adding 1mA to the over-scale threshold that
you select (this could be as high as 30mA depending on your selection of over-
scale threshold).
Loop Power Supply Voltage:
Make sure your voltage level is at least 9V plus
0.020*load_resistance. Ideally, it should be great enough to drive the over-
range alarm current into your load (i.e. up to 9V+ 0.030*Rload, assuming line
drop is negligible and the maximum possible over-range threshold is
configured). The non-volatile memory of the transmitter receives its power
from the loop supply, not USB. Therefore, apply power to the transmitter
output loop and always power the loop before connecting to USB.
3. Connect to PC via USB:
Refer to USB Connections of page 11 and connect the
transmitter to the PC using the USB isolator and cables provided in
Configuration Kit TTC-SIP.
Now that you have made your connections and applied power, you can
execute the TT231Config.exe software to begin configuration of your unit
(software is compatible with XP or later versions of the Windows operating
system).
Connect Input
Connect Output
Connect PC/USB
Configure
Calibrate I/O