Four quadrant control of DC Motors
Model 2761 Signal Isolation Amplifier
Model 2761CT Current Sensing Isolation Amplifier


• Dual AC input power voltage selection, 115/230 VAC, 50/60 Hz
•1500 VDC Isolation
• Excellent linearity: 0.1% typical
• Accepts voltage or current signals
• Optional current sensing feature
• Customer selectable jumpers
• Five input voltage ranges: 200mV, 1V, 5V, 10V, 100V
• Three input current ranges: 1~5mA, 4~20mA, 10~50mA
• Four optional current sensing ranges: 10A, 20A, 50A, 100A
• Two on-board trimpots: offset, range
• Manual external pot set-up capability
• DIN-RAIL mounted enclosure
• Accepts floating or grounded signal inputs
• Temperature operating range: 0~70°C

The MODEL 2761 Signal Isolation Amplifier provides complete electrical isolation between signal input voltages or currents derived from programmable controllers, process transducers such as light, pressure, and temperature. The amplifier can also accept an analog signal from a digital-to-analog converter. The output of the Isolation Amplifier is connected to the input of any variable speed motor control with an analog input capability. The maximum output voltage of the Isolation Amplifier is ±10 VDC, which is a linear function to the input signal.

The Model 2761 Signal Isolation Amplifier can accommodate a wide range of input voltages (±200mV, ±1V, ±5V, ±10V, ±100V) and, in addition, a wide range of input current signals (1~5mA, 4~20mA, 10~50mA).

The Isolation Amplifier can be set-up as a manual master control by wiring a 10K ohm master potentiometer as follows: CW terminal to reference output terminal, wiper terminal to signal input, CCW terminal to input common.

This Isolation Amplifier can be used as an armature voltage follower. Setting the amplifier up in this configuration will allow you to control one motor speed in proportion to that of an independent DC motor. The signal input would be derived from the voltage across the armature of the master motor, since speed is proportional to the voltage. The amplifier should be set-up for the ± 100 VDC setting for 90 VDC rated motors. If more than one slave motor speed controller is to follow the output from a single master amplifier, setting the ratio between two or more of the motor speeds can be accomplished with ratioing pots.

Board mounted trimpots provide the scaling ability required to match a given range of input signal with the desired range of output voltage. the range adjustment trimpot sets the amplifier output when the maximum signal input is applied. The offset trimpot provides nulling the output voltage when signal input applied is calling for 0 VDC output.

The MODEL 2761 CT Isolation Amplifier has an optional current sensing feature with the following ranges: 10A, 20A, 50A, 100A. The amplifier provides the precision, stability, and isolation needed to accurately monitor motor current in high noise motor control environments. The amplifier can also be used for general purpose industrial current sensing that requires isolation. The maximum output voltage is ±10 VDC, which is a linear function of the current.