Hampshire Controls Corp.
1 Grove St.
Dover, NH 03820
(603) 749-9424 or Toll Free US/Canada (866) 496-9424
www.hampshirecontrols.com
LD-215 Liquid Nitrogen Level Sensor
User Instructions
Overview of Operation
The
LD-215
uses a cryogenic RTD to sense the surface of
liquid nitrogen by monitoring the self-heating of the probe. The
alarm will sound and the output relay will change state when the
liquid level drops below the probe tip. In reverse mode, the
alarm will sound and the output relay will change state if the
liquid level makes contact with the probe tip.
The alarm can be silenced for a selectable period of time by
pressing the
“MUTE” button. During mute the “ALARM” LED
will continue to flash and the
output relay will stay in the “alarm”
condition. A return to normal liquid level will clear the alarm. See
page 2 for mute duration adjustment.
An alarm delay can also be specified. After the unit recognizes
an alarm condition, the green status
“TIMING” LED will switch to
yellow and the unit will delay for the selected period before
alarming. See page 2 for alarm delay adjustment.
Any alarm condition, muted or not, will cause the relay to switch
to alarm state. The user can wire to the “Normally Open” (NO,
closed on alarm) or “Normally Closed” (NC, open on alarm)
contacts for external dialers, or other functionality.
Setting the Trip Point (Calibration)
Make sure the probe tip is fully submerged in liquid Nitrogen, wait 2 minutes for the probe temperature to
fully stabilize, press the
RED
push-button twice (pictured below). Observe the
“TIMING” LED flash green
7 times to confirm successful setting of the new setpoint.
