The ips120 module

Basic drivers for an Oxford Instruments model IPS120

Note that this module does not represent an Instrument subclass, since the IPS120 is never used by itself—it is always part of a larger system driving both a magnet power supply and temperature controllers, and the power supply often cannot be used in an isolated way.

Classes

IPS120

class src.instruments.noauto.ips120.IPS120(name='Magnet', protocol='ISOBUS', isobusAddress='0', visaAddress='GPIB0::23', serialConfig=None)

This is a basic driver for an Oxford Instruments model IPS120 power supply. It should be included in an Instrument class representing a cryostat-magnet system.

Parameters :

name : str

A name to identify the instrument

protocol : {‘ISOBUS’, ‘GPIB’, ‘Serial’, ‘Gateway Master’, ‘Gateway Slave’}

The protocol for communication between the computer and the power supply.

isobusAddress : str

An integer string representing the ISOBUS address, if relevant. An integer will be accepted and converted.

visaAddress : str

A full VISA resource address (including the bus) to locate the instrument (e.g. “GPIB0::27”).

serialConfig : dict

A dictionary to indicate how to configure a serial port, which is used with both the ‘ISOBUS’ and ‘Serial’ protocols.

Methods

getField()

Return the magnetic field in Tesla.

Returns :

float :

The magnetic field in Tesla.

getFieldSetpoint()

Return the field setpoint in Tesla.

Returns :

float :

The magnetic field setpoint.

getStatus()

Update the power supply status.

Read the power supply status, and set the local variables to reflect the new status.

Notes

The power supply returns a string of the form XmnAnCnHnMmnPmn. The meanings and values of the parts of this are described here.

Xmn: System status

m: Status 1

• 0: Normal
• 1: Quenched
• 2: Over-heated
• 4: Warming up
• 8: Fault

n: Status 2

• 0: Normal
• 1: On positive voltage limit
• 2: On negative voltage limit
• 4: Outside negative current limit
• 8: Outside positive current limit

An: Activity

• 0: Hold
• 1: To setpoint
• 2: To zero
• 4: Output clamped

Cn: Control status

• 0: Local and locked
• 1: Remote and locked
• 2: Local and unlocked
• 3: Remote and unlocked
• 4: Auto-run-down
• 5: Auto-run-down
• 6: Auto-run-down
• 7: Auto-run-down

Hn: Switch heater status

• 0: Off—magnet at zero (switch closed)
• 1: On (switch open)
• 2: Off—magnet at field (switch closed)
• 5: Heater fault (heater is on, but current is low)
• 8: No switch fitted

Mmn: Mode

m: Mode 1

• 0: Amps, Fast
• 1: Tesla, Fast
• 4: Amps, Slow
• 5: Tesla, Slow

n: Mode 2

• 0: At rest (output constant)
• 1: Sweeping (output changing)
• 2: Rate limiting (output changing)
• 3: Sweeping and rate limiting (output changing)

Pmn: Polarity

m: Polarity 1 (see below)

• 0: pos, pos, pos
• 1: pos, pos, neg
• 2: pos, neg, pos
• 3: pos, neg, neg
• 4: neg, pos, pos
• 5: neg, pos, neg
• 6: neg, neg, pos
• 7: neg, neg, neg

n: Polarity 2 (verification flags)

• 1: Negative contactor closed
• 2: Positive contactor closed
• 3: Both contactors open
• 4: Both contactors closed

Note

Unlike with the PS120, with the IPS120, Immediate mode is indicated by Mode 2 returning the value ‘2’ (sweep limiting, but not sweeping); it does not have its own flag.

Note

For the IPS power supplied, the polarity flags have been superceded by signed numbers for currents and fields.

getSweepRate()

Return the field sweep rate in Tesla/min.

Returns :

float :

The magnetic field sweep rate in Tesla/min.

initialize()

Prepare the power supply for use.

Prepare the power supply for use by

1. opening the appropriate communication channel;
2. setting the control mode to ‘remote and unlocked’;
3. setting the activity to ‘hold’;
4. setting the polarity to ‘forward’;
5. setting the sweep rate to 0.5 T/min;
6. setting the sweep mode to ‘Tesla, sweep, fast’; and
7. setting the switch heater to ‘Off, magnet at zero’.

setActivity(activity='0')

Set the activity mode of the power supply.

Parameters :

activity : str

An integer string representing the desired activity. The accepted values are listed below.

• ‘0’: Hold at current field (default).
• ‘1’: Ramp the field to the setpoint.
• ‘2’: Ramp the field to zero.
• ‘4’: Clamp the output.

setControlMode(controlMode='3')

Set the control mode for the power supply.

Parameters :

controlMode : str, optional

An integer string representing the desired control mode. Allowed values are the following.

• ‘0’: Local and locked (power-up state).
• ‘1’: Remote and locked.
• ‘2’: Local and unlocked.
• ‘3’: Remote and unlocked (default).

setField(field)

Set the magnetic field in Tesla.

Parameters :

field : float

The magnetic field setpoint in Tesla.

setPolarity(polarity='0')

Set the power supply polarity.

Parameters :

polarity : str

A string containing a single integer representing the desired polarity (or polarity-changing action). The following values are accepted.

• ‘0’: Do nothing (default).
• ‘1’: Set the polarity to forward.
• ‘2’: Set the polarity to reverse.
• ‘4’: Swap the polarity.

.. note:: This method is included for backward compatibility. The :

polarity has been deprecated in favor of signed numbers for the field or current setpoints.

setSweepMode(sweepMode='9')

Set the power supply’s sweep mode.

The power supply’s sweep mode consists of two parameters:

Display:

The instrument’s front-panel display units (amps or tesla)

Magnet sweep rate:

One of two user-defined sweep profiles: “fast” and “slow”; the “fast” mode is entered upon power supply startup. The names have no significance, and the actual rates are user-defined variables.

Parameters :

sweepMode : str, optional

The integer string code to specify the sweep mode of the power supply. The allowed codes are the following.

• 0: Amps, Fast
• 1: Tesla, Fast
• 4: Amps, Slow
• 5: Tesla, Slow
• 8: Amps, Unaffected
• 9: Tesla, Unaffected

setSweepRate(sweepRate=0.5)

Set the magnetic field sweep rate in Tesla/min.

Parameters :

sweepRate : float, optional

The desired sweep rate for the magnet in Tesla/min (default 0.5).

setSwitchHeater(heaterStatus='0', delay=20.0)

Set the status of the switch heater.

Turn the switch heater on or off, optionally checking whether it is safe to do so. Then wait a specified amount of time for the power supply to carry out the command.

Parameters :

heaterStatus : {‘0’, ‘1’, ‘2’}, optional

An integer string representing the desired switch heater status. The following values are accepted.

• ‘0’: Turn the heater off (default).
• ‘1’: Turn the heater on if the power supply current and the magnet current are equal. Otherwise, do nothing.
• ‘2’: Turn the heater on without checking the currents.

delay : float, optional

The time to wait (in seconds) after commanding the switch heater to adopt the specified status. The value should be at least 15s.