Our VAS is used to activate another process in response to a customer specified
voltage between 30 and 1000 volts rms. We use back-to-back MOSFET's mounted
inside the sensor as the switching element. When the AC voltage being monitored
reaches or exceeds the switch setting the MOSFET's conduct to activate
another AC or DC control circuit connected to that switch. The VAS uses
a transformer which has been optimized with external circuitry for sensing
of potential while drawing a minimum of power. It will typically draw less
than 2mA from the voltage being monitored. The controlled circuit is fully
isolated from the input and will switch up to 250 watts in any AC or DC
control circuit. Continious current through closed output contacts can
be up to 2.4 amps (at lower switchingvoltage). Reactive loads are allowed.
The output circuit will remain on at any moderate voltage above the switch setting (with no damage to the switch), and then turn off as the voltage falls below 10% of the turn on setting.
Example:
If you want the VAS to turn on at 100 volts it will stay on until the
voltage drops back to 90 volts or less, at 200 volts it will turn off at
180 volts. This hysteresis is required to prevent chattering between the
on and off state. Standard SRT policy on all of our VAS's is to use a hysteresis
of 10%, but this can be changed moderately to accommodate customer requirements.
These units have consistent switching repeatability and are easy to retro-fit to an existing system, or they can be implemented into a variety of new systems. Applications can include computerized Building Control Systems (BCS), Energy Management Systems (EMS), and safety shutdown control of systems.
Engineers at SRT are available to discuss any questions you might have on any of our products. Often we are asked to customize or prepare special calibrations on our sensors to suit customer needs. Please contact us at (800) 447-6805 and ask for Dayle Smith or Doug McNutt, or FAX us at (719) 634-2601, or send E-mail to sales@srt-inc.com.
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