7B33 Isolated, Voltage or Current Input


Model 7b33-01-1The 7B33 is a single-channel signal conditioning module that interfaces, amplifies and filters unipolar voltage inputs and provides a protected precision output of either +1 V to +5 V or 0 V to +10 V. To measure a process current input, a plug-on 250 Ω current sensing resistor, Model AC1391, may be installed directly on the 7B backplane, using available pin sockets. The external current sense resistor allows the current loop to be maintained even when the module is removed from the backplane. Model 7B33 features a nonlinearity of ±0.02% maximum and an accuracy of ±0.1% maximum (±0.01% typical). 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 105 dB @ 50/60 Hz is provided. Rated to operate with a nominal +24 V DC supply, Model 7B33 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 7B33 Series Module

The two input pins of Model 7B33 are fully protected up to 120 V rms line voltage. A one-pole 100 Hz filter preconditions the input signal prior to amplification 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 @100 Hz), a buffer amplifier and a power oscillator. The two-pole output filter and subsequent buffer ensures that a low noise, low impedance (<1 Ω) signal is available at the output to drive loads of 2 kΩ minimum.

Input and Output Ranges


Figure 1. 7B33 Functional Block Diagram


Figure 2. 7B33 Input Field Connections

Input Types Output Options
4 mA to 20 mA
0 to 20 mA
+1 V to +5 V
0 V to +10 V

View and Order Models

  Model  Input Range
Output Range 
Order Now
7B33-01-1 +1 V to +5 V +1 V to +5 V
Order Now
0 V to +5 V
0 V to +10 V
Order Now  7B33-01-1 +4 mA to +20 mA1 +1 V to +5 V 
Order Now
7B33-01-2 0 mA to +20 mA1   0 V to +10 V 


7B33 Specifications
(typical @ +23°C ±5°C and Vs = +24 V dc)

Model 7B33 
Input Range1
Standard Ranges
+1 V to +5 V; 0 V to +5 V
(Refer to Model Table)
Custom Ranges
Not Available*
Output Range Options (RL > 2 kΩ)
+1 V to +5 V or 0 V to +10 V
Initial @ +25°C
±0.01% Span (±0.1% Span, maximum)
±0.02% Span, maximum
Input Offset vs. Temperature
Span vs. Temperature
±15 ppm/°C
Output Offset vs. Temperature
±0.003% span/°C
Input Bias Current
±0.1 nA
 Input Resistance
Power ON
2 MΩ
Power OFF
30 kΩ, minimum
 Output Noise
5 MHz Bandwidth
6 mV peak
10 Hz to 100 kHz Bandwidth
0.4 mV rms
0.1 Hz to 10 Hz Bandwidth
4 µV peak
Bandwidth, -3 dB 100 Hz
Output Rise Time, 10% to 90% Span
10 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
105 dB
Input Protection
120 V rms, continuous
±35 V dc, continuous
Input Transient Protection
ANSI/IEEE C376.90.1-1989
IEC 255-4, Class II
Output Resistance
< 1 Ω
Voltage Output Protection
Continuous Short to Ground
 Power Supply
Voltage Range, Operating
+14 V dc to +35 V dc
+20 mA, maximum
±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)
60 grams
Temperature Range
-40°C to +85°C
  Storage -40°C to +85°C
Relative Humidity, 24 hours
0 to 90% @ +60°C 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.
1 Model 7B33 may be used to measure a process current input by installing a 250 Ω current sensing resistor, such as Model AC1391, on the backplane. With this resistor, the current loop is maintained even when the 7B33 module is removed from the backplane.
2 Includes the combined effects of repeatability, hysteresis, and nonlinearity.
3 Nonlinearity is calculated using best-fit straight line method.
4 Input offset term is included in the output offset specification.
Specifications subject to change without notice.