Model DT335-0700
Dual RTD/Resistance Input Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 33 -
http://www.acromag.com
- 33 -
https://www.acromag.com
Inputs...continued
Input Resolution:
The ADC
’s
of this model will divide the input signal range into the
number of parts that can be calculated using the expression for ADC counts as
32768*R
IN
*Gain/499, with Gain=1 for all input types except Copper RTD uses Gain=16
(resistance of input sensor is R
IN)
. The number of parts between the nominal input
range low and high endpoints shown in the following table.
Table 2 - Input Resolution per Input Type
Input Type
α Alpha
1
ADC Input Resolution
Pt 100Ω, 200Ω, 500Ω, 1000Ω
0.00385
1 part in 24425
0.00390
1 part in 24714
0.003911
1 part in 24812
0.00392
1 part in 24868
Ni 120Ω (Minco 7
-120)
0.006872
1 part in 26569
Cu 10Ω (Minco 16
-9)
0.004274
1 part in 19384
Resistance (0 to 25 Ohms)
N/A
1 part in 26172
Resistance (450, 900, 2250, 4500 Ohms)
N/A
1 part in 29491
Notes (Table 2):
1
Alpha (α) is used to identify the RTD curve. Refer to “RTD Resistance
versus Temperature” section for an explanation of alpha value.
This transmitter
allows a portion of the nominal input range to be rescaled to the output range
selected. However, the effective input resolution will be proportionally diminished as
the span is reduced. The effective I/O resolution of this transmitter will be the lowest
resolution of the ADC itself, its normalization to ±25000, or the output DAC (output
DAC is 1 part in 46984 for 4-20mA).
Input Zero and Full-Scale Adjustment:
Nominal input ranges are selectable and
range endpoints are adjustable over the full range of input temperature/resistance.
Input Zero and Full-Scale selections must be within the nominal range and will be
mapped to zero/0% and full-scale/100% at the output. Keep in mind that the input
resolution diminishes below nominal as a programmed range is reduced. Likewise,
error is magnified as input span is reduced.
Outputs (Each)
Unit outputs are short-circuit
protected from damage.
Output Range:
Each channel has separate voltage and current output terminals that
share a common return. Only one output signal of a channel, voltage or current, may
be loaded at one time. See Table 3 for supported output ranges with over-range.
Output Accuracy:
Better than
0.05% of span, typical, and ±0.1% maximum, with
nominal input and output ranges. This includes the effects of repeatability, terminal
point conformity, and linearization, but does not include sensor error.
Output Noise/Ripple:
Less than
0.1% of output span, typical.
Note (High Speed Acquisition w/current output):
Additional filtering is recommended
at the load for sensitive applications with high-speed acquisition rates. For excessive
60Hz supply ripple and current output, a 1uF or larger bulk capacitor is recommended
at the load. High frequency noise is often reduced or eliminated by placing a 0.1uF or
0.01uF capacitor directly across the load (this can also raise RF immunity).
Output Ambient Temperature Effect:
Better than
80ppm/
C (±0.0080%/
C) over
the ambient temperature range. This includes the combined effect of zero and span
drift for reference test conditions (see Input Specifications).
Output Resolution:
Each output is driven by a 16-bit voltage/current DAC from Texas
Instruments (DAC8760IPWPR) and its nominal range resolution is indicated in Table 3
below. The effective I/O resolution of a channel will be the lowest resolution of the
input A/D or output D/A relative to the selected and scaled I/O range.