5B32 Isolated Current Input


Model 5B32-02The 5B32 is a single-channel signal conditioning module that amplifies, protects, filters and isolates its analog input. The module measures a process-current input signal of 4-20 mA or 0-20 mA by reading the voltage across an external precision 20 Ω resistor (supplied) and generating an output of 0 to +5 V. Extra current conversion resistors are available as accessories (See Model AC1362 in the Accessories section).

Note that the 5B32 module circuitry can withstand 240 V rms at the input screw-terminals, thereby shielding computer-side circuitry from field-side overvoltage conditions. In addition, all 5B32 Series modules are mix-and-match and hot swappable, so can be inserted or removed from any socket in the same backplane without powering down the system.

Inside the 5B32 Series Module

A chopper-stabilized input amplifier provides low drift and stable gain. At the amplifier input, a stable, laser-trimmed zero-scale input offset is subtracted from the input signal to set the zero-scale value for the 4-20 mA range. For user convenience, the zero can be optionally factory-set to meet custom needs. This allows suppression of a zero-scale input value many times larger than the total span for precise expanded-scale measurements.

Internal multi-pole lowpass filtering with a four-Hz cutoff (-3dB) enhances normal-mode (noise on signal) and common-mode (noise on signal return) rejection at 50/60 Hz, enabling accurate measurement of small signals in high electrical noise.

Signal isolation by transformer coupling uses a proprietary modulation technique for linear, stable and reliable performance. The differential input circuit on the field side is fully floating, eliminating the need for input grounding. A demodulator on the computer side of the signal transformer recovers the original signal, which is then filtered and buffered to provide a low-noise, low-impedance output signal. The output common must be kept within ±3 Vdc of power common.

Convenience Features 

A series output switch eliminates the need for external multiplexing in many applications. The switch is turned on by an active-low enable input. If the switch is to be on at all times, the enable-input should be grounded to power common as it is on the 5B01 and 5B08 backplanes.

Input and Output Ranges

5B32 Functional Block Diagram

Figure 1. 5B32 Functional Block Diagram

5B32 Input Field Connections
Figure 2. 5B32 Input Field Connections

Input Ranges
Output Ranges
4 mA to 20 mA
0 to +5 V
(-5 V to +5 V ­ custom)

5B32 Models Available

Model  Input
Order Now 5B32-01
4 mA to 20 mA 0 V to +5 V
Order Now 5B32-02
0 mA to 20 mAV
0 V to +5 V


* Custom Input/Output ranges are available. Refer to configuration guide.

5B32 Specifications

Description  Model 5B32
Input Ranges
Standard Ranges
0 mA to 20 mA or 4 mA to 20 mA
Custom Ranges
0 mA to 20 mA (refer to ordering section)
Output Ranges (RL > 50 kΩ)4
-5 V to +5 V or 0 V to +5 V
Initial @ +25°C
±0.05% Span ±0.05% Iz1
±0.02% Span
Input Offset vs. Temperature
±0.0025 of Iz/°C
Output Offset vs. Temperature
±20 µV/°C
Gain vs. Temperature
±0.0025% of Reading/°C
Input Resistor5
Value 20.0 Ω
Accuracy ±0.1%
Stability vs. Temperature ±0.001%/°C
Input, 0.1 Hz to 10 Hz Bandwidth
10 nA rms
Output, 100 kHz Bandwidth
200 µV rms
Bandwidth, -3 dB 4 Hz
Output Rise Time, 10% to 90% Span
200 ms
Common-Mode Voltage (CMV)3
Input-to-Output, Continuous
1500 V rms maximum
Output-to-Power, Continuous
±3 V maximum
Transient ANSI/IEEE C37.90.1-1989
Common-Mode Rejection (CMR)
1 kΩ Source Imbalance, 50/60 Hz
160 dB
Normal Mode Rejection 50/60 Hz
60 dB
Input Protection
240 V rms maximum
ANSI/IEEE C37.90.1-1989
Output Resistance4
50 Ω
Voltage Output Protection
Continuous Short to Ground
Output Selection Time 6 µs @ Cload = 0 to 2,000 pF
Output Enable Control
Max Logic "0"  +1 V
Min Logic "1"
+2.5 V
Max Logic "1"
+36 V
Input Current "0"
0.4 mA
Power Supply Voltage
+5 V ±5%
Power Supply Current 30 mA
Power Supply Sensitivity, RTI
±2 µV/Vs%
Mechanical Dimensions
2.275" x 2.375" x 0.595"
(57.8 mm x 59.1 mm x 15.1 mm)
Temperature Range
   Rated Performance -25°C to +85°C
   Operating -40°C to +85°C
   Storage -40°C to +85°C
Relative Humidity
0 to 93% @ +40°C noncondensing
RFI Susceptibility
±0.5% Span error @ 400 MHz, 5 Watt, 3 ft

1 Iz is the nominal input current that results in a 0 V output.
2 Includes the combined effects of repeatability, hysteresis, and nonlinearity and assumes RL > 50 kΩ. Does not include current-to-voltage input resistor (AC1362) error.
3 The output common must be kept within ±3 V of power common.
4 Loads heavier than 50 kΩ will degrade nonlinearity and gain temperature coefficient.
5 The current-to-voltage conversion resistor (AC1362) is supplied as a plug-in component for mounting external to the module. All backplanes and mounting cards provide pin sockets for mounting the AC1362 resistor.

Specifications subject to change without notice.