RS Technologies


	Quad Wheel SCU

Click here to download a complete brochure on the Quad Wheel SCU in PDF form.

Quad Wheel Signal Conditioning Unit

The Quad Wheel Signal Conditioning Unit (SCU) measures torque, speed, and angular position on a four‑wheeled vehicle equipped with appropriate wheel.The Quad Wheel SCU provides excitation and pre‑amplifier functions for strain gage-based torque wheel transducers. Five-volt excitation is also provided for operating the magnetic two-track angular position encoder.

Torque is measured with 1 mV/V full-scale nominal transducer sensitivity. With 1400 ohm bridges, a 437.1k ohm shunt calibration resistor produces approximately 0.8 mV/V. Pre‑amp gain is normally set up for 5.00 volts full scale output. Since transducers are available in 50,000 and 75,000 lb‑in capacities, the calibration certificates provide the exact full scale values and shunt calibration simulation values for each wheel.

Speed is measured using encoder “A” track 720 pulses per revolution. Calibration is achieved using a 12,000 Hz signal to simulate 1000 rpm.Angular position is measured using “A” and “B” tracks 720 pulses per revolution. Maximum resolution is achieved with quadrature counting 2880 zero crossings per revolution providing 1/8-degree resolution.

Physical Description

The following tables describe the display, controls, and connections of the quad wheel signal-conditioning unit.

Front Panel Display and Controls

Display	4 ½ character LCD
Calibrate	Pushbutton to activate the calibration mode for the selected channel.
Calibration Mode	LED to indicate when unit is in the calibration mode. In the calibration mode, the shunt calibration resistors are connected by the calibration relays on all four torque channels simultaneously. RPM calibration requires that a TTL 50% duty cycle square wave input be applied to the rpm calibration BNC on the connector panel. The calibration pushbutton switch must be placed in the ON position, which disconnects the encoders and simultaneously connects the calibration frequency signal to all four rpm circuits. The Signal Selector switch, described below, is used to select which wheel sensor is displayed.
Signal Sector	Selects a channel for display. Torque channels are as follows: T1 for channel #1, LF; T2 for channel #2, RF; T3 for channel #3, LR; T4 for channel #4, RR. Speed Channels are as follows: S1 for channel #1, LF; S2 for channel #2, RF; S3 for channel #3, LR; S4 for channel #4, RR.
Calibration Zero and Gain Adjustments	These potentiometers are located under the protective panel and can be accessed by loosening the captive screw.

Side Panel Connections

Sensor Inputs	Accepts input from wheel sensors (Bendix PTO2A‑12‑10S) using following pin assignments.
Torque Outputs	Provides 0 to ±5 volt FS (Bendix PTO2A‑12‑8S) using the following pin assignments.
Speed Outputs	Provides 0 to +5 volts FS (Bendix PTO2A‑10‑6S) using the following pin assignments.
Encoder Outputs	A‑B track Quadrature, 0 to 5 volt logic output (Bendix PTO2A‑12‑10S) using the following pin assignments.
Power Switch	Turns unit on.
Fuse	3 amp to protect internal circuitry.
Power Input (12 vdc)	Automobile battery input, 10 to 15 vdc.
Voltmeter	Parallel connection to internal switched meter.
RPM CAL	BNC connector to supply 12 kHz signal to calibrate speed circuitry.
GND	Analog common, 12 volt negative.

Working hard to meet RoHS requirements for a safer, cleaner environment!