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Model 302 EXPv1 Stacking Process Control Expansion Board for expandable Model 302

connection diagram


similar expansion board for 3-axis motor control


2  PDr2 Proportional Valve Drivers, both normally OFF (DAC channels 1 & 2)

1  unassigned buffered 5V reference output

1  set of three terminals for string pot connection (A/D channel 2)

1  set of three terminals for RTD or thermistor connection (A/D channels 3 & 4)

1  isolated input F-to-V converter (A/D channel 1)

8  250 ma current sink digital outputs for driving solid state relays, etc.

1  PWM output from DAC 3

Connector for jumpers to send power to the M302 board

4  tie point terminals for V+ connection for poppet valves, relays, etc.

Analog input features can be bypassed

2  spare terminals, plus a prototyping area

The EXPv1 expansion board stacks on the expandable version of the Model 302 Data Acquisition System. The Expansion board contains a mixture of interfacing circuitry suitable for a wide variety of acquisition and control applications. Inputs can be voltage, current, frequency, or resistance, with accomodation for RTD or thermistor temperature sensors. Analog Outputs can be voltage, current, or PWM. The optically isolated current outputs can sink 2 amps or more. Digital outputs can sink up to 250 ma.

The individual interfacing blocks are based on proven, high performance products and are designed for use with our 24-bit data acquisition systems. High impedance analog inputs interface directly to ion selective and pH electrodes. High resolution allows direct interfacing to bridge sensors or even thermocouples.

Proportional Valve Drivers, two available

Two proportional drive circuits are provided. They are optically isolated power drivers for solenoids, valves, DC heaters, DC motors, and other DC loads. They output a proportional current from 0 to 2.5 amps, or more. The current output follows an analog voltage from analog outputs 1 and 2 on the Model 302 data system.

A proportional valve, a fan motor, and a heating element are examples of loads that can be controlled with resolution matching the analog control voltage. Expensive loop controllers can be replaced with improved performance and much lower cost in many applications.

Output up to 2 amps, or more, at 10 to 24 volts, optically isolated

Input control voltage 0-5 volts

Efficient, so that no active cooling is needed.

Typical modulation frequency 1500 Hz or 4000 Hz factory option

Modulation frequency is preset, but can be set over a wide range

Load can be inductive or resistive

Built-in 5 amp freewheeling diode for inductive loads

Gain is adjustable via on-board trim potentiometer, 0 - 100% range

Output is monotonic

Linearity is excellent over the middle 90% of the range

Counts-to-Volts input, one available

A frequency or pulse stream can be converted to a precise analog voltage. Resolution is good enough to see a single edge while still being able to handle 100s of kHz. The input can be from any sort of pulse or frequency generator, including position sensors and radiation detectors. A proprietary Sigma-Delta demodulation approach is used for superior accuracy and stability.

18 bit resolution, high stability counts-to-volts converter

Optical isolation on input

Dual sensitivity ranges

Edge triggered, duty-cycle independent

0.25 second time constant

See the Model 106 for more details

Digital Outputs
Eight current sink outputs are provided. These accommodate up to 30 volts at 250ma continuous current. 100% overcurrent can be sustained for a fraction of a second.

PWM Output
Analog output number 3 is available as a duty cycle on a screw terminal on the the expansion card.

Other Input
Circuitry and connection points are provided for RTD or thermistor inputs. Connections provided for string potentiometer or other ratiometric inputs. Power connections are provided for powering a bridge circuit or other powered sensor.

Power Requirement
The expansion card is powered from the Model 302's power supply. It requires less than 30 ma, so the smallest supplies are adequate. Loads can be be powered by the same supply, if sufficient, or by external isolated or unisolated power sources.

The system is designed to be easy to customize. Contact the factory for a different mix of features, or entirely new capabilities.

Starting Price


Contact us for sales or technical assistance   lawsnlab@lawsonlabs.com

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