Model TT231-0600
Two-Wire RTD Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 17 - http://www.acromag.com
- 17 -
http://www.acromag.com
Configuration…
HELP
– You can press F1 for Help
on a selected or highlighted field
or control. You can also click the
[?] button in the upper-right hand
corner of the screen and click to
point to a field or control to get a
Help message pertaining to the
item you pointed to.
Select the Sensor Wiring…
This selection tells the unit which inputs to connect to its internal PGA, and which
inputs to connect its excitation sources to.
If you select
“Two-Wire”
, your input measurement will not be compensated for
the sensor lead resistance, and your input range zero will be fixed at 0°C (Pt
RTD). S
ensor leads less than a few feet long will have negligible resistance,
minimizing the importance of lead-wire compensation in these applications.
If you select
“Three-Wire”
, your input measurement will be compensated for
its lead-wire resistance, as long as the ± input leads are of the same length, size,
and type. Additionally, you will be able to select an input zero of -50°C, 0°C, or
0°F (input zero is a fixed selection of 3 different values, while the full-scale is
programmable to any value in range). If you have a four-wire sensor, select
“Three-Wire”.
A selection of “Two Wire” requires that you additionally wire input terminals 3
& 4 together with a short copper jumper wire. A selection of “Three Wire”
requires that a third lead be wired to input terminal 4 and the other end of this
lead connects to the minus terminal at the sensor. In both cases, this “third-
wire” connection serves as the return path for the excitation current and it must
be present in either form, in order to make your measurement. If you have
actually wired a four-wire sensor, it will use 3-wire lead compensation.
Select the Alpha Value…
(Pt RTD Only, for internal use only)
For the Pt RTD Input Type, you should specify the
Alpha Value
of your particular
RTD curve. The software only uses this information to compute the input
resistances required to calibrate your selected input range for Platinum RTD Input
Types, which it then returns in message prompts during the calibration process. If
you are calibrating to a particular curve not indicated, you may select this value
arbitrarily and just substitute your own resistance values during calibration that will
correspond to your particular curve at the temperatures noted.
Note:
1
Alpha (
) is used to identify the RTD curve and its value is derived by dividing
the sensor resistance at 100
C (boiling point of water) minus the sensor resistance at
0ºC (freezing point of water), by the sensor resistance at 0
C, then by 100
C (
=
[R
100
C -
R
0
C
] / R
0
C
/ 100
C). For Pt 100
, this is 38.5
/100.0
/100
C, or
0.00385
/
/
C, and represents the average change in resistance per ºC.
Select the Temperature Units…
(Pt RTD Only)
For your input range, select the temperature units in degrees Celsius or degrees
Fahrenheit. Note that input ranges specified in degrees Fahrenheit will have a fixed
input range zero of 0°F. Units in °C can chose an input range zero of -50°C or 0°C.