Model TT231-0600
Two-Wire RTD Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 36 - http://www.acromag.com
- 36 -
http://www.acromag.com
Input…
Notes (Table 1):
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 0°C
(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 °C.
2
The Zero of the range is a fixed choice of -50°, 0°C, or 0°F for 3-wire RTD. The 2-wire
RTD input uses a fixed zero of 0°C.
3
Rated accuracy applies for input spans greater than 50°C or 8Ω, and with a 16mA
output span.
Input Configuration:
Three-wire w/ lead compensation, four-wire w/ 3-wire lead
compensation, or two-wire w/o lead compensation.
Input Zero Adjust:
For Pt RTD w/ 3 or 4-wire connection, select
-50°C, -17.78°C (0°F), or 0°C, or for Pt RTD w/2-wire Connection, input zero is fixed at
0°C. For Resistance input, zero is user-specified in ohms, as 0Ω or 100Ω typical.
Some zero values in ohms will not be acceptable and the software may prompt you
to make adjustments.
Input Full-Scale Adjust:
For Pt RTD, specify a full-scale temperature up to 850°C. For
Resistance input, specify a resistance up to 900Ω. Minimum recommended span is
50°C (RTD), and 8Ω (Resistance).
Input Response Time:
See Output Response Time.
Input Filter Bandwidth:
-3dB at 700Hz, typical, normal mode filter.
Input Linearization:
Preset for input. Additive to excitation current to accomplish
linearization of Pt RTD inputs. Correction is digitally adjustable with an 8-bit value
(256 steps), at 3.9nA/mV per step (set to zero for linear resistance input). The
maximum linearization coefficient is 0.99uA/mv (∆Iref/∆Vin).
Input Gain:
PGA gain is adjustable for 6.25, 12.5, 25, 50, 100, 200, and 400 mV/mV.
PGA output voltage sinks current through 6.34KΩ and a current gain of 50mA/mA is
applied to that current at the output stage.
Input Excitation Current:
Utilizes dual current sources, one for each ± input lead,
matched within ±0.2%. Set to 0.493mA typical, with less than 10ppm/°C drift over
temperature (zero code level for each is between 0.480mA and 0.510mA). Digitally
adjustable via Coarse and Fine DAC’s with 256 steps of adjustment for each (7bits +
sign bit). Coarse adjust is -195 to +195uA w/1.54uA/step. Fine adjust is -12.2 to
+12.2 uA with 96nA/step. Also adjusted via linearization feedback for Pt RTD input
types.
Input Lead-Wire Compensation:
Requires balanced ± sensor leads (same size,
length, & type) and only used with 3 or 4-wire sensor connections. Recommended
maximum lead resistance is 25
per lead.
Input Lead Resistance Effect:
Shift less than ±0.01% per ohm of lead resistance, with
a max shift less than ±0.1% with up to 10Ω per ±lead.
Lead Break/Sensor Burnout Detection
: Select output upscale or downscale
detection. Alarm output level is indirectly programmed via the linear U/O threshold
settings (see Output Fault Limits).
Input Bias Current:
50pA typical (PGA), ~doubling every +10°C.