Model TT231-0600
Two-Wire RTD Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 18 - http://www.acromag.com
- 18 -
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 Input Range Zero and Input Range Full-Scale…
Next you need to select the input temperature range for the Pt RTD Input Type, or
your input resistance range for the Resistance Input Type.
Your selection of
Input Zero
is the RTD temperature or input resistance that will
correspond to 0% of output. For Platinum RTD types, use the scroll bar to select
your
Input Zero
temperature: -50°C, 0°C, or 0°F (Zero is a fixed value for Pt RTD).
For Resistance Input Type, you instead enter an
Input Zero
value in ohms (0Ω
typical, for a 0-500Ω range, or 100Ω typical for a 100-200Ω range). If you choose 0Ω
as your input zero, then your under-scale threshold selection set in a later step
cannot be achieved, except for the purpose of indirectly setting the downscale
alarm limit, which is ~0.4mA below your under-scale threshold setting.
Note that when setting your range, some under-range is built-in later via the Under-
scale Threshold selection set separately (see below).
Note that this selection indirectly determines the PGA minus lead connection from
the input multiplexer. Different paths are chosen which have different pedestal
resistors installed that happen to be set just below the corresponding resistance of
the platinum input sensor at its zero temperature. For example, the Resistance Input
Type will use the 0°C pedestal resistor which is 98.8Ω. An equivalent sensor input
resistance actually drives the differential signal measurement to 0V.
Next, enter your Input Full-Scale temperature (Pt RTD Input), or full-scale resistance
(Resistance Input Type). Your Input Full-Scale selection will correspond to 100% of
output. For Pt RTD, you can enter any value up to 850°C. For the Resistance input
type, you can enter any resistance value up to 900Ω. Note that the unit does
convert under-range and over-range values outside of the 0% and 100% limits, and
this is set by separately selecting the output Under/Over-scale Thresholds.
Not all combinations of Input Zero and Input Full-Scale will be possible. The
software may prompt you to make another selection. Also, if the input zero and full-
scale points are chosen too close together, performance will be degraded. A
minimum span of 50°C is recommended. Note that you will have to be able to
precisely drive the corresponding input range resistance values for zero and full-
scale in order to calibrate your input range later.
Select the Output Range Zero and Output Range Full-Scale…
In the
Output Zero
and
Output Full-Scale
fields, enter the output currents that are
to correspond to 0% and 100% of output respectively. This is typically 4mA and
20mA, respectively, but you could optionally specify an output zero from 3.5mA up
to 6.0mA, or an output full-scale from 16mA up to 24mA. Note that the output
range over-scale and under-scale thresholds are specified separately and will
determine the linear operating range of the output including possible over/under-
range outside of these approximate limits.
If the output zero and full-scale points are chosen too close together, performance
will be degraded. Use input spans greater than 50°C.