Model DT33x-0700
4-Wire DC I/V Dual Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 31 -
http://www.acromag.com
- 31 -
https://www.acromag.com
Input...continued
Analog to Digital Converter (A/D):
Each input channel uses a 24-bit,
-
A/D
converter with only the first 16-bits used. Its signal is normalized to a bipolar range
count of ±25000 to simplify I/O scaling (see Resolution below).
Sampling Rate (A/D):
ADC Inputs are sampled at a variable rate with filter as follows:
A/D SAMPLING RATE (SAMPLES/SECOND) PER INPUT FILTER
NONE
LOW
MED
HIGH
214.65sps
53.6625sps
13.42sps
1.6775sps
Input Impedance:
Each channel has two input circuit paths A & B that support
different ranges. Input impedance will vary with the input path divider as follows:
INPUT IMPEDANCE PER MODEL INPUT PATH DIVIDER
MODEL
INPUT PATH A
INPUT PATH B
DT336-0700
24.9Ω
Current Shunt
No Divider
1
, 15MΩ
DT337-0700
No Divider
1
, 15MΩ
86.6K/(998K+86.6K),
1MΩ
DT338-0700
28K/(499K+28K),
500KΩ
5.36K/(998K+5.36K)
, 1MΩ
1
Note:
Direct connection to A/D channel without a resistive divider.
Input Overvoltage Protection:
Inputs include Bipolar Transient Voltage Suppressers
and diode clamping along with series resistance and capacitive filtering.
Input Filter:
RC filtering plus digital filtering, optimized and fixed per input range and
filter selection within the
-
ADC. See also Normal Mode Noise Rejection and
Output Response Time.
Input Noise Rejection (Common Mode):
Varies with filter selection between no
filtering and high filtering as follows (data is measured with a 100
input unbalance):
Typical Common Mode Noise Rejection
MODEL
NO FILTER
HIGH FILTER
DT33x
100dB
120dB
Input Noise Rejection (Normal Mode):
Varies with input filter level and input path
divider. The minimum measured rejection of the DT336 model is given which does
not divide its inputs. The higher rejection of the DT337 & DT338 is estimated by
adding 20*log[input_divider] (see Input Resolution for applicable dividers per input
path).
Typical 60Hz Rejection for Input Path A & B per Input Filter Setting
MODEL
None (dB)
Low (dB)
Med
1
(dB)
High
1
(dB)
DT336
A, B: 7
A, B: 25
> 80dB
1
> 80dB
1
DT337 est
A: 7, B: 29
A: 25, B: 47
> 80dB
1
> 80dB
1
DT338 est
A: 32, B: 52
A: 50, B: 70
> 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.
Bandwidth:
The frequency where the DT336 is attenuated 3dB for each input filter
level setting is shown below (DT337 & DT338 similar). See also Normal Mode Noise
Rejection and Output Response Time.
Bandwidth (-3dB) per Input Filter Setting
MODEL
None (dB)
Low (dB)
Med (dB)
High (dB)
DT336
34Hz
18Hz
12Hz
1.4Hz
