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Overview / Design Principle:
This recorder is a potentiometer-type controller designed for use with porportional positioning motors to operate modulating valves or damper systems where extremely close sensitivity or straight-line control is required.
The instrument automatically positions any of a variety of standard motor operators to provide precise temperature control without sawtooth line characteristics of conventional on-off control. Flush or wall mounted, brackets supplied. Available in 12 optional ranges from -30ºF to 1100ºF. CSA listed.
Operation:
The potentiometer coil, which moves up or down scale in response to the expansion or contraction in the thermal element, also slides the contact finger along the potentiometer coil within the modulating range.
In essence, the coil forms half of a Wheatstone Bridge circuit, while the other half of the bridge is formed by a potentiometer of similar electrical characteristics built into the proportioning motor and driven by the motor shaft.
When the contact finger is located at the low end of the potentiometer coil as in process start-up, the motro drives the device to the fully open position.
With the contact finger at the high end of the coil, the motor moves the drive to the fully closed position.
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