Group3 Hall Probe

-	-
IOC	G3HALLPR
OPI	Group3 Hall Probe
Manual	\\isis\shares\ISIS_Experiment_Controls\Manuals\Group3__Hall_Probe

Description

This is a hall probe IOC, which is used as part of HIFI's zero-field system. The HIFI zero-field uses two devices (and correspondingly, will use two G3HALLPR IOCs), which are on separate serial ports.

Each IOC can talk to 3 probes, which can be named via the NAME0..NAME2 macros (e.g. X or -Y).

A multiplier can be set for each field via the SCALE0..SCALE2 macros (usually this will be either 1 or -1).

The scan rate for both field and temperature are independently specified as IOC macros.

State machine

An SNL program is in use to automatically change the measurement range of each probe.

The thresholds at which this SNL program moves up/down a range are specified in PVs of the form $(P)$(SENSORID):STATEMACHINE:R0:UP - which in this case would be the threshold, in Gauss, at which to move up from r0 (Range 0, 0.3 Tesla) to r1 (Range 1, 0.6 Tesla). These thresholds may be modified via PV sets in the configuration, if needed.

To allow the device to settle in a new range, there is also a minimum delay after changing states before the next state change - this is in PVs of the form $(P)$(SENSORID):STATEMACHINE:STATE_CHANGE_DELAY, which again can be modified by PV sets in the configuration if desired. By default it is 2 seconds.