210-421-A General Purpose Temperature Alarm

The 210-421-A Temperature Alarm is a microprocessor-based, dual-setpoint alarm suitable for environmental and industrial applications. It can also be configured as a frost alarm. The alarm sounds and controls the operation of two electrical circuits when the temperature reaches either of the two independently set limits. The temperature range is -40 °F to 160 °F (-40 °C to 71 °C), as is the alarm range. The alarms can be configured to trigger based on temperatures greater than or less than the setpoint. A liquid crystal display provides a readout of the measured temperatures and displays maximum and minimum temperatures, as well as the values of various alarm parameters, via a series of setup menus.

Self-contained relays can be used for each alarm point to actuate external devices, such as small pumps or sirens. These relays can also control external power relays for switching high current loads. The 210-421-A also includes an audible alarm that can be silenced if desired. To prevent erratic or premature operation of controlled devices, the 210-421-A allows you to set a delay or confirmation interval before initiating an alarm, as well as a delay time before negating an alarm.

All setpoints and maximum and minimum temperature values are stored in non-volatile memory, ensuring that these values are not lost in the event of a power failure. The circuits are designed to have high electrical noise immunity against transient spikes generated when loads are switched with the alarm relays. After a power failure, the unit restarts in running mode.

The temperature sensing probe is based on a precision thermistor and is designed to measure over a wide range of temperatures. The 380-280 Solar Radiation Shield is recommended for use with the air temperature probe in outdoor applications.