fsc2: 6.5 Gaussmeter Functions

6.5 Gaussmeter Functions

Currently, the following gaussmeters are implemented:

bh15: Bruker BH15, Hall probe controller
er035m: Bruker ER035M, NMR gaussmeter accessed via GPIB and used as field controller
er035m_s: Bruker ER035M, NMR gaussmeter accessed via serial port and used as field controller
er035m_sa: Bruker ER035M, NMR gaussmeter accessed via GPIB and used as stand-alone device
er035m_sas: Bruker ER035M, NMR gaussmeter accessed via serial port and used as stand-alone device
pt2025: Metrolab PT2025, NMR gaussmeter
bnm12: Bruker BNM12, NMR gaussmeter

To use a module in an experiment put its name into the DEVICES section of the EDL script.

The range of fields that can be measured with the Bruker ER035M NMR gaussmeter depends on the probe being used. With the F0 probe (S-band) the range is 460 G to 2390 G while with the F1 probe (X-band) a range between 1460 G and 19900 G can be measured. With the BH15 field controller a range between -50 G and 2300 G can be used. Finally, for the Metrolab PT2025 it is currently assumed that a probe for the field range between 1.5 T and 3.4 T (W-band) is used.

The modules with names starting with er035m are for the Bruker ER035M NMR gaussmeter. er035m and er035m_sa are to be used when the device is controlled via the GPIB bus while er035m_s and er035m_sas expect the device to be connected to a serial port of the computer. (Should you be wondering why there are versions for both GPIB and the serial port, the explanation is that some of the ER035M gaussmeters simple don't seem to work with the GPIB bus even though they should.) The bh15 module is for the Hall controller used in some setups, the pt2025 module is for the Metrolab 2025 NMR gaussmeter. The last module, bnm12, is for the Bruker BNM12 gaussmeter.

Please note:: The Bruker BH15 Hall field controller can also be used to directly control the field of a magnet by outputting an appropriate voltage to be used as the controlling input for a magnet power supply. For this purpose a different module exists, bh15_fc. The module bh15 described in this section only supports the use of the device as a gaussmeter.

The three gaussmeter modules, er035m, er035m_s and bh15 can be used in conjunction with the modules for controlling a magnet, aeg_s_band and aeg_x_band. In that case the gaussmeter module to be used for this purpose must be listed in the DEVICES section before the magnet module that relies on it and, if more than one of these gaussmeter modules is to be used, as the first gaussmeter module.

The remaining modules, er035m_sa, er035m_sas, pt2025 and bnm12, are only to be used for field measurements but are not involved in field control.

The Bruker BNM12 NMR gaussmeter can only be read out when the Wasco WITIO-48 DIO card and the home-built DA/AD converter are available and their modules have already been loaded.

List of gaussmeter functions:

`gaussmeter_name()'
`gaussmeter_field()'
`gaussmeter_resolution()'
`gaussmeter_probe_orientation()'
`gaussmeter_upper_search_limit()'
`gaussmeter_lower_search_limit()'
`gaussmeter_keep_going_on_field_error()'
`gaussmeter_keep_going_on_error()'
`find_field() (deprecated)'
`measure_field() (deprecated)'

Descriptions of gaussmeter functions:

`gaussmeter_name()'

Returns a string with the name of the gaussmeter being used.

`gaussmeter_field()'

The function returns the current field in Gauss. It takes no arguments and can only be used in the EXPERIMENT section.

Please note:: For the Bruker BNM12 NMR gaussmeter with a field resolution setting of 0.01 G the kG part of the field value gets cut off, i.e. with this resolution setting a field of 3125.63 G will be reported as being 123.63 G.

`gaussmeter_resolution()'

This function exists for the modules for the Bruker NMR gaussmeters (er035m, er035m_s, er035m_sa and er035m_sas), the Metrolab 2025 NMR gaussmeter and for the Bruker BNM12 NMR gaussmeter. It can be used to set or query the resolution in Gauss used in measurements of the magnetic field.

To set a resolution the values 0.1 G, 0.01 G and 0.001 G can be used for the Bruker NMR gaussmeters. For the Metrolab 2025 gaussmeter only 0.01 G and 0.001 G are usable. Finally, for the Bruker BNM12 NMR gaussmeter the values 1.0 G, 0.1 G and 0.01 G can be used.

Please note:: For the modules er035m and er035m_s, i.e. the modules for direct field control, the resolution will be increased automatically from 0.1 G to 0.01 G at the initialization (i.e. at the very start of the experiment) unless the low resolution has been set explicitely during the PREPARATIONS section.
Also note: for the Bruker BNM12 gaussmeter changing the resolution won't effect the device directly, it can only be read out. The device has a switch at its front panel where the resolution can be set and calling this function is for making the module aware of the setting of the switch (its position can't be determined from within the program). This is necessary to be able to interpret the data received from the device correctly. Per default the module will assume that the resolution is set to 0.1 G.

`gaussmeter_probe_orientation()'

This function is currently implemented for the Metrolab 2025 NMR gaussmeter pt2025 and the the Bruker NMR gaussmeters (er035m, er035m_s, er035m_sa and er035m_sas). It allows to query the current probe orientation relative to the field, returning either 1 or 0 for an orientation parallel or anti-parallel to the field.

For the Metrolab 2025 it can also be used to change the orientation to parallel to the field by calling it with an argument of 1 or "+" and anti-parallel with an agument of 0 or "-".

The function can only be called in the EXPERIMENT section.

`gaussmeter_upper_search_limit()'

This function can be called to set of query the upper search limit (in Gauss) for the modules er035m, er035m_s, er035m_sa and er035m_sas. The function can only be called in the EXPERIMENT section.

`gaussmeter_lower_search_limit()'

This function can be called to set of query the lower search limit (in Gauss) for the modules er035m, er035m_s, er035m_sa and er035m_sas. The function can only be called in the EXPERIMENT section.

`gaussmeter_keep_going_on_field_error()'

This function only exists for the Bruker NMR gauss-meters that don't are used for controlling the field ("stand alone" modules), er035m_sa and er035m_sas. When the lock on the field is lost and the module fails to reestablish it, or when the field is too unstabe to be measured, the function for measuring the field normally aborts the EDL script. In some cases this can be detrimental since measuring the field is not always essential and aborting the whole experiment might be over-kill. To avoid that this function can be called (without any arguments). Once it has been called (somewhere in the EXPERIMENT section when the function gaussmeter_field() detects that the lock on the field has lost and can't be reestablished, it only prints out a warning and returns -1.0 as the field value instead of aborting.

`gaussmeter_keep_going_on_field_error()'

This function only exists for the Bruker NMR gauss-meters that don't are used for controlling the field ("stand alone" modules), er035m_sa and er035m_sas. These devices sometimes don't react as they're supposed to (e.g. requests to send the current field value don't return a value at all or communication with the device fails) which normally results in the experiment getting stopped. But in some situations it's preferable to continue the experiment, even though a function calls didn't return the expected value. And for such situations this function can be used to set what is suposed to happen.

If called with the string "STOP" (or the integer 1) the device behaves as usual, i.e. on all errors the experiment is stopped. If called with "CONTINUE" (or 1) the failed function returns -1, and so will all further calls of gaussmeter functions. If called with "RETRY" (or 2) the failed function also returns -1, but on further calls of gaussmeter function another attempt will be made to communicate with the device.

If called without an argument the function returns an integer, indicating the currently set behaviour.

`find_field()'

Use of this function is deprecated, use gaussmeter_field() instead.

`measure_field()'

Use of this function is deprecated, use gaussmeter_field() instead.

This document was generated by Jens Thoms Toerring on September 6, 2017 using texi2html 1.82.