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Functional Description
 The 7B34 is a single-channel
signal conditioning module that interfaces, amplifies and
filters input voltages from a wide variety of two- and three-wire
platinum, copper and nickel Resistor Temperature Detectors
(RTDs) and provides a protected precision output of either
+1 V to +5 V or 0 V to +10 V, linear with RTD temperature.
Three-wire lead resistance compensation is provided and
2- or 3- wire RTDs may be used. RTD excitation current,
and a predictable upscale open circuit indication provide
a complete signal conditioning solution. Model 7B34 features
a nonlinearity of ±0.05% maximum (Pt RTDs). To accurately
measure low level signals in electrically noisy environments,
1500 V rms of galvanic transformer-based isolation with
a common mode rejection (CMR) of 160 dB @ 50/60 Hz and a
normal model rejection (NMR) of 60 dB @ 50/60 Hz are provided.
Rated to operate with a nominal +24 V DC supply, Model 7B34
is mix-and-match and hot-swappable with other 7B Series
input modules, so it can be inserted or removed from any
socket in the same backplane without disturbing system power.
Inside the 7B34 Series Module
The three input pins of Model 7B34 are fully protected up
to 120 V rms line voltage. A 250 µA excitation current
is provided to create an input voltage to the 7B34. This
current also provides the upscale open circuit indication.
A one-pole 3 Hz filter preconditions the RTD signal prior
to amplification, provided by a low drift input amplifier.
Amplitude modulation is used to implement transformer isolation
(1500 V rms input-to-output and power). Isolated front-end
circuitry power is supplied by a DC/DC converter. The output
section contains a two-pole low pass filter (-3 dB @ 3Hz),
a buffer amplifier and a power oscillator. The two-pole
output filter and subsequent buffer ensures that a low noise,
low impedance (<1  )
signal is available at the output to drive loads to 2 kminimum.
Figure 1. 7B34 Functional Block diagram
Input Types
- 100 Platinum
RTDs
- 120 Nickel
RTDs
- 50 Copper
RTDs
Output Options
- +1 V to +5 V
- 0 V to +10 V
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Figure 2. 7B34 Input Field Connections
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7B34 Models Available
| Model |
RTD Sensor
(2- or 3-wire) |
Input Range |
Output Range |
Nonlinearity
(maximum) |
Accuracy
(maximum) |
|
7B34-01-1
|
100 Pt,
 =
0.00385 |
-100℃ to +100℃ |
+1 V to +5 V |
±0.05% span |
±0.15% span |
|
7B34-01-2
|
100 Pt,
=
0.00385 |
-100℃ to +100℃ |
0 V to +10 V |
±0.05% span |
±0.15% span |
|
7B34-02-1
|
100 Pt,
=
0.00385 |
0℃ to +100℃ |
+1 V to +5 V |
±0.05% span |
±0.2% span |
|
7B34-02-2
|
100 Pt,
=
0.00385 |
0℃ to +100℃ |
0 V to +10 V |
±0.05% span |
±0.2% span |
|
7B34-03-1
|
100 Pt,
=
0.00385 |
0℃ to +200℃ |
+1 V to +5 V |
±0.05% span |
±0.15% span |
|
7B34-03-2
|
100 Pt,
=
0.00385 |
0℃ to +200℃ |
0 V to +10 V |
±0.05% span |
±0.15% span |
|
7B34-04-1
|
100 Pt,
=
0.00385 |
0℃ to +600℃ |
+1 V to +5 V |
±0.05% span |
±0.1% span |
|
7B34-04-2
|
100 Pt,
=
0.00385 |
0℃ to +600℃ |
0 V to +10 V |
±0.05% span |
±0.1% span |
|
7B34-N-01-1
|
120 Ni,
=
0.00672 |
0℃ to +300℃ |
+1 V to +5 V |
±0.12% span |
±0.3% span |
|
7B34-N-01-2
|
120 Ni,
=
0.00672 |
0℃ to +300℃ |
0 V to +10 V |
±0.12% span |
±0.3% span |
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7B34-N-02-1
|
120 Ni,
=
0.00672 |
0℃ to +200℃ |
+1 V to +5 V |
±0.14% span |
±0.3% span |
|
7B34-N-02-2
|
120 Ni,
=
0.00672 |
0℃ to +200℃ |
0 V to +10 V |
±0.14% span |
±0.3% span |
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7B34-C50-01-1
|
50 Cu,
=
0.00214 |
-100℃ to +100℃ |
+1 V to +5 V |
±0.10% span |
±0.15% span |
|
7B34-C50-02-1
|
50 Cu,
=
0.00214 |
0℃ to +100℃ |
+1 V to +5 V |
±0.02% span |
±0.15% span |
|
7B34-C50-06-1
|
50 Cu,
=
0.00214 |
-50℃ to +200℃ |
+1 V to +5 V |
±0.08% span |
±0.15% span |
7B34 Specifications
(typical @ +23℃ ±5℃ and Vs
= +24 V dc)
| Description |
Model 7B34 |
| Input Range1 |
| RTD Types |
100 Platinum,
2-, 3-wire = 0.00385 |
|
|
120 Nickel,
2-, 3-wire, = 0.00672 |
| Standard Temperature Ranges |
Refer to Model Table |
| Custom Ranges |
Not Available* |
| Output Range Options (RL
> 2 k) |
+1 V to +5 V or 0 V to +10 V |
| Accuracy1 |
| Initial @ +25℃ |
Refer to Model Table |
| Nonlinearity2 |
Refer to Model Table |
| Input Offset vs. Temperature |
±1 µV/℃ |
| Zero Suppression vs. Temperature |
±0.002% (Rz/Rspan)3/℃ |
| Span vs. Temperature |
±60 ppm/℃ |
| Output Offset vs. Temperature |
±0.002% Span/℃ |
| Lead Resistance Effect |
±0.02℃/ |
| Output Noise |
| 5 MHz Bandwidth |
10 mV peak |
| 10 Hz to 100 kHz Bandwidth |
0.4 mV rms |
| 0.1 Hz to 10 Hz Bandwidth |
0.6 µV peak |
| Bandwidth, -3 dB |
3 Hz |
| Output Rise Time, 10% to 90% Span |
250 ms |
| Common-Mode Voltage (CMV) |
| Input-to-Output and Power |
1500 V rms, continuous |
| Common Mode Rejection (CMR) |
| Input-to-Output and Power @ 50/60 Hz |
160 dB |
| Normal Mode Rejection @ 50/60 Hz |
60 dB |
| Input Protection |
120 V rms, continuous
±35 V dc, continuous |
| Input Transient Protection |
ANSI/IEEE C376.90.1-1989
IEEE-STD 472
IEC 255-4, Class II |
| Output Resistance |
< 1 |
| Voltage Output Protection |
Continuous Short to Ground |
Power Supply |
| Voltage Range, Operating |
+14 V dc to +35 V dc |
| Current |
+25 mA, maximum |
| Sensitivity |
±0.0001%/% of Vs |
| Mechanical dimensions |
1.663" x 2.11" x 0.563"
(42.24 mm x 53.6 mm x 14.3 mm) |
| Weight |
60 grams |
Environmental |
| Temperature Range |
| Operating |
-40℃ to +85℃ |
| Storage |
-40℃ to +85℃ |
| Relative Humidity, 24 hours |
0 to 90% @ +60℃ noncondensing |
| ESD Sensitivity |
IEC 801-2, Level 2 |
| RFI Susceptibility |
±0.5% Span error @ 400 MHz, 5 Watt, 3 ft |
Warm-up time required to meet specifications
is approximately 10 minutes.
* Contact factory for OEM requirements.
1Includes the combined effects of repeatability, hysteresis,
and nonlinearity.
2Nonlinearity is calculated using best-fit straight line
method.
3Rz is the value of the RTD resistance at the lowest
measurement point. Rspan is the change in
resistance over the measurement span.
Specifications subject to change without notice. |
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