3B17 WIDE BANDWIDTH, LVDT/RVDT INPUT

Functional Description

The 3B17 is a wide-bandwidth single-channel signal- conditioning module which isolates, amplifies, and filters signals from 4-, 5-, or 6-wire Linear Variable Displacement Transformers (LVDTs) or Rotary Variable Displacement Transformers (RVDT). The 3B17 input module provides an AC excitation voltage of 1 V rms to 5 V rms at frequencies between 1 kHz and 10 kHz. All gain and zero suppression can be user-calibrated by screwdriver adjustments through the sliding door on the top of the module. Gain can vary over an extensive 256:1 range by adjusting a combination of a rotary switch and trim potentiometer. Zero suppression can vary over ±5 V from the center setting. The current output can be independently adjusted over a ±5% range for zero and span. In addition, the 3B17 is mix-and-match and hot-swappable with all 3B Series modules, so it can be inserted or removed from any socket in the same backplane without disrupting system power.

3B Series Custom-Ranging Program

Externally-programmable versions, Models 3B17-00 and 3B17-D-00, enable the user to configure a special input range, excitation voltage and excitation frequency by using the optional plug-on AC1310 ranging card, which houses user-supplied resistors to determine excitation voltage amplitude and frequency. To facilitate selecting resistors, a Windows^® program, 3B-CUSTOM, calculates resistor values based on the user-desired input/output ranges and AC excitation.

Inside the 3B17 Series Module

The 3B17 input and AC excitation output terminals are protected for up to 130 V rms, protecting the computer side from damage due to field-side overvoltage faults. The LVDT input signal is amplified to give the high level output voltage. The 3B17 automatically compensates for phase errors between the primary and secondaries of the LVDT or RVDT, eliminating the need for a phase adjustment, and automatically rejects any residual quadrature voltages via a unique approach to error compensation which uses the sum of the two secondary windings to directly drive the demodulator. The amplitude and frequency of the AC excitation can be factory configured to meet custom needs (Model 3B17-CUSTOM) or externally configured (Models 3B17-00 and 3B17-D-00) with the optional AC1310 plug-on custom ranging card.

Figure 1. 3B17 Functional Block Diagram

Figure 2. 3B17 Input Field Connections

3B17 Models Available

3B17 Specifications
(typical @ +25°C and ±15 V dc, and +24 V dc Power)

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 3B17-00 model, using the AC1310 ranging card.
⁵ Bandwidth can be set for up to 1/10 the excitation frequency when ordering Model 3B17-custom.
⁶ +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.
⁷ Typical supply current is ±40 mA per module plus ±5 mA for the LVDT drive current. To calculate supply current requirements from LVDT currents, use 75% of the LVDT rms current.
Specifications subject to change without notice.