Model DT333-0700
4-Wire mV/TC Dual Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 31 -
http://www.acromag.com
- 31 -
https://www.acromag.com
Input...continued
NOTE:
For best accuracy
and performance, mount
this unit upright on a DIN
rail and allow free air flow
intake from the bottom
vent to flow through the
unit and out the top vent.
This will allow unit to run
cooler, helping to extend
the life of the electronics.
It will also increase CJC
accuracy for TC inputs.
Input Thermocouple CJC Reference (TC Input Only):
Table 2 below shows the accuracy of
the CJC sensors used in TB1 and TB3. CJC has been factory calibrated at 25°C to ±0.1°C and
its accuracy over the full operating range will be about ±1.0°C.
Table 2: Thermocouple CJC
1
Sensor Absolute Accuracy
CJC Range
Typical
Maximum
25°C
±0.1°C
±0.3°C
10 to 80°C
±0.3°C
±0.6°C
-40 to 80°C
±0.5°C
±1.2°C
1
Note:
Cold Junction Compensation (CJC) may be switched OFF to permit direct connection
of an input millivolt signal via copper wires to simplify calibration. Otherwise a hand-held
calibrator may be used. For best results, allow the module to warm-up to thermal
equilibrium for 5-10 minutes prior to calibrating CJC. During calibration, physically position
the module the same as its field application (recommended upright on a DIN rail). Note that
the input is normally calibrated with CJC OFF, and CJC calibration is done separately.
Input Linearization (T/C Inputs):
Within
0.25
C of the NIST tables.
Input Break Detection
: Set Upscale or Downscale if an input sensor opens or a lead breaks
(limits are output range dependent). The upscale limit is approximately 24mA, 11V, or 5.5V.
Downscale output limit is approximately 0mA, -11V, or -5.5V. Note that selecting a reverse-
acting output will flip the output break detent (but not the input reading).
IMPORTANT:
Calibration should be done with break detection already set as required by
the application, as changing it will affect calibration somewhat.
Input Bias Current
: ±125nA typical (TC break current).
Input Analog to Digital Converters (A/D):
Inputs each utilize 24-bit,
-
A/D converters,
with only the first 16-bits used. The A/D signal is then normalized to a bipolar range count
of ±25000 to simplify I/O scaling (see Input Resolution below).
Sampling Rate (A/D):
Inputs sampled at a variable rate with filter as follows:
A/D SAMPLING RATE (SAMPLES/SECOND) PER INPUT FILTER
MODEL
None
Low
Med
High
DT333
107.325sps
26.83125sps
6.71sps
0.83875sps
Input Impedance:
15.4MΩ, typical.
Input Overvoltage Protection:
Inputs include Bipolar Transient Voltage Suppression (TVS)
and diode-clamping along with series resistance and capacitive filtering.
Input Filter:
Normal mode RC filtering, plus digital filtering, optimized and fixed per filter
selection within the
-
ADC. See Normal Mode Noise Rejection and Response Time.
Input Noise Rejection (Common Mode):
Varies with input filter selection between no filter
and high filter as follows (data measured with a 100
input unbalance):
Typical Common Mode Noise Rejection
MODEL
None
High
DT333
96dB
134dB
Noise Rejection (Normal Mode):
Varies with input filter level.
Typical 60Hz Rejection per Input Filter Setting
MODEL
None (dB)
Low (dB)
Med
1
(dB)
High
1
(dB)
DT333
0.12dB
24dB
> 80dB
1
> 80dB
1
1
Note:
At medium and high filter settings, the heavily attenuated 60Hz signal cannot be
measured due to 4
th
order filtering by the input ADC which adds 80dB minimum of rejection
at frequencies between 47Hz and 61Hz.
