Functional Description

The 3B18 is a wideband (20 kHz) single-channel signal conditioning module which interfaces, amplifies, and filters signals from balanced 4-arm full-bridge strain-gage bridges with a resistance from 100 Ω to 10 kΩ, providing simultaneous precision voltage and current outputs. The module provides two user-selectable (via front-panel switches) bridge excitation voltages: +10 V for bridges with a load impedance down to 300 Ω or +3.33 V for 120 Ω bridges or others below 300 Ω. Module bandwidth is also user-selectable between 20 kHz and 100 Hz, with user-supplied filter capacitors installed in the optional AC1310 ranging card. The 3B18 protects the computer side from damage due to field-side overvoltage faults up to 130 V rms. In addition, the current output withstands 130 V rms without damage and interfaces user equipment through screw terminals located on the 3B Series backplane. The 3B18 is a plug-in, mix-and-match, hot-swappable module which is easily field calibrated via front-panel zero and span adjustments for both voltage and current outputs.

3B Series Custom-Ranging Program

Externally-programmable Model 3B18-00, 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 3B18 Series Module

A chopper-stabilized low-drift (±1µV/°C) input amplifier assures stable long-term stability. For user convenience, the zero and span can be factory configured to meet custom range needs (Model 3B18-CUSTOM) or can be externally programmed (Model 3B18-00) via user supplied resistors inserted in the optional AC1310 plug-on ranging card.


Figure 1. 3B18 Functional Block Diagram

3B18 WIP

Figure 2. 3B18 Input Field Connections


Input Type

Strain Gage:

Full 4-Arm Bridge

Dual Outputs

-10 V to +10 V

4 mA to 20 mA or 0 to 20 mA

3B18 Models Available

  Model Input
Excitation1 Sensitivity Output
Order Now 3B18-00 Full
+10.0 V or +3.33 V Externally
-10 V to +10 V &
0 mA to 20 mA
Order Now 3B18-01 Full
-30 mV to +30 mV +10.0 V or +3.33 V 3 mV/V @ 10 Vexc -10 V to +10 V &
0 mA to 20 mA
Order Now 3B18-02 Full
-10 mV to +10 mV +10.0 V or +3.33 V 3 mV/V @ 3.33 Vexc -10 V to +10 V &
0 mA to 20 mA
  3B18-Custom Full Bridge * +10.0 V or +3.33 V * *
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.

3B18 Specifications
(typical @ +25°C and ±15 V dc, and +24 V dc Power)

Description Model 3B18
Input Range
Standard Range ±30 mV (3 mV/V sensitivity @ Vexc = +10V)
±10 mV (3 mV/V sensitivity @ Vexc = +3.33 V)
Custom Ranges ±5 mV to ±500
Output Range
Voltage (RL > 2 KΩ) -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
Initial @ +25°C ±0.1% Span
Nonlinearity2 ±0.01% Span
Stability vs. Temperature
Voltage Output
   Zero ±3 µV/°C (RTI)
   Span ±25 ppm of Reading/°C
Current Output3
   Zero ±25 ppm of Span/°C
   Span ±25 ppm of Reading/°C
Bridge Excitation
Voltage user-selectable +10 V or +3.33 V
Voltage, tolerance ±2%
Voltage vs. Temperature ±0.0015%/°C
Bridge Resistance Range
Vexc= +10.0 V 300 Ω to 1 kΩ
Vexc = +3.33 V 100 Ω to 10 kΩ
Zero and Span Adjustment Range4 ±5% of Span
Input Bias Current +25 nA
Input Resistance 100 MΩ
Bandwidth, -3 dB 20 kHz
Output Rise Time, 10% to 90% Span 24µs
Common-Mode Voltage (CMV)
Input-to-Output, Continuous ±10 V peak, maximum
Transient ANSI/IEEE C37.90.1- 1989
Common Mode Rejection (CMR)
1 kΩ Source Imbalance, 50/60 Hz 100 dB
Input Protection, Signal and Excitation Voltage
Continuous 130 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 ±(13.5 V dc to 16.5 V dc)
   Current +50 mA, -15 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)
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 mA 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 3B18-00 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.
Specifications subject to change without notice.

Send Feedback X
content here.
content here.

Send Feedback