3B32 Isolated, Process Current Input

The 3B32 is a single-channel signal conditioning module that interfaces, amplifies and filters a process-current input and provides simultaneous precision output voltage and current. Process-current input signals are measured by reading the voltage across an external precision 100 Ω resistor (supplied). Model 3B32 performs complete signal conditioning, including isolating (±1500 V peak input-to-output and power) and protecting their computer side outputs from damage and loss of signal integrity, and shielding their inputs from damage from field-side overvoltage faults up to 220 V rms. The current output withstands 130 V rms without damage and interfaces user equipment through screw terminals located on the 3B Series backplane. Each plug-in, mix-and-match, hot-swappable module is easily field calibrated via front-panel zero and span adjustments for both voltage and current outputs.

3B Series Custom-Ranging Program

Externally-programmable version, Model 3B32-00, enables the user to configure a special input range by using the optional plug-on AC1310 ranging card, which houses user-supplied resistors to determine zero and span. To facilitate selecting resistors, a Windows^® program, 3B-CUSTOM, calculates resistor values based on the user-desired input/output ranges.

Inside the 3B32 Module

A chopper-stabilized low-drift (±1µV/°C) input amplifier assures stable long-term stability. At the amplifier input, a stable, zero-scale input voltage is subtracted from the input signal to set the zero-scale value. Zero suppression can exceed 100% of the input range. This is ideal for expanded-scale applications requiring high-resolution measurement of a selected portion of an input signal. For user convenience, the zero and span can be factory configured to meet custom range needs (Model 3B32-CUSTOM) or can be externally programmed (Model 3B32-00) via user supplied resistors inserted in the optional AC1310 plug-on ranging card. Internal lowpass filtering with a 3 Hz cutoff (-3 dB) two-pole Butterworth filter enhances both 60 dB normal-mode and 160 dB common-mode rejection at 50/60 Hz, enabling accurate measurement of small signals in high electrical noise.

Signal isolation is accomplished by transformer coupling with 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 any input grounding. A demodulator on the computer side of the signal transformer recovers the original signal, which is then filtered and buffered and drives a voltage-to-current (V/I) converter to provide the current output.

Figure 1. 3B32 Functional Block Diagram

Figure 2. 3B32 Input Field Connections

Input Type	Dual Outputs
4 mA to 20 mA	0 to +10 V
0 to 20 mA	0 to 20 mA or 4 to 20 mA

	Model	Input Range	Output Ranges1
Order Now	3B32-00	Externally Programmable2	-10 V to ±10 V & 0 mA to 20 mA
Order Now	3B32-01	4 mA to 20 mA	0 V to ±10 V & 4 mA to 20 mA
Order Now	3B32-02	0 mA to 20 mA	0 V to ±10 V & 4 mA to 20 mA
	3B20-Custom	*	*

¹ Output current range may be user programmed to 4 mA to 20 mA using jumper supplied.
² Requires AC1310 ranging card.
* Custom Input/Output ranges are available. Refer to configuration guide.

(typical @ +25°C and ±15 V dc, and +24 V dc Power)

Description	Model 3B32
Input Range
Standard Ranges	0 mA to 20 mA; 4 mA to 20 mA
Custom Ranges	0 mA to 20 mA (refer to ordering section)
Output Range
Voltage (RL > 2 KΩ)	0 V to +10 V; -10 V to +10 V
Current (RL = 0 to 850Ω)1	4 mA to 20 mA or 0 mA to 20 mA
Maximum Current Output Span	0 mA to 31 mA
Accuracy2
Initial @ +25°C	±0.1% Span
Nonlinearity2	±0.01% Span
Stability vs. Temperature
Voltage Output
Zero	±25 ppm of Span/°C
Span	±25 ppm of Reading/°C
Current Output3
Zero	±25 ppm of Span/°C
Span	±25 ppm of Reading/°C
Zero and Span Adjustment Range4	±5% of Span
Input Resistor
Value	100 Ω
Accuracy	±0.1%
Stability vs. Temperature	±0.002%/°C
Input Bias Current	+3 nA
Input Resistance (Module)	15 MΩ
Noise
Input, 0.1 Hz to 10 Hz Bandwidth	0.2 µV rms
Output, 100 kHz Bandwidth	50 µV rms
Bandwidth, -3 dB	3 Hz
Output Rise Time, 10% to 90% Span	200 ms
Common Mode Voltage (CMV)
Input-to-Output, Continuous	±1500 V peak, 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
Continuous	220 V rms maximum
Transient	ANSI/IEEE C37.90.1-1989
Voltage Output Protection	Continuous Short to Ground
Current Output Protection	130 V rms, continuous
Power Supply Voltages5
±15 V dc Supplies
Rated Operation	±(11.5 V dc to 16.5 V dc)
Current	±10 mA
Sensitivity	±0.01% span/V
+24 V dc Loop Supply
Rated Operation	+12 V dc to +30 V dc
Current	+27 mA @ lout = 20 mA
Sensitivity	±0.0002% span/V
Mechanical Dimensions	3.15" x 3.395" x 0.775" (80.0 mm x 86.2 mm x 19.7 mm)
Environmental
Temperature Range
Rated Performance	-25°C to +85°C
Storage	-55°C to +85°C
Relative Humidity, 24 hours	0 to 95% @ +60°C noncondensing
RFI Susceptibility	±0.5% Span error @ 400 MHz, 5 Watt, 3 ft

¹ For a 0 to 20 mA range, a typical minimum output current is 10 µA.
² Includes the combined effects of repeatability, hysteresis, and nonlinearity.
³ With respect to the voltage output.
⁴ A wide range of custom zero suppression and span is available with the 3B32-00 model, using the AC1310 ranging card.
⁵ +24 V dc loop power is required for driving the current output at loads up to 850Ω. If a current output load of 400Ω or less is applied, +15 V dc is sufficient for loop power. If only voltage output is used, loop power is not required.