QZFM analog output configuration

[Oleg Shevtsov]

Dear James and other team members

We works with gen.2 and gen.3 dual axis sensors together with a data acquisition unit (NI-9205) to record the signal from the analog output. Recording is done in a shielded room (no active field compensation system).

As can be seen from the recordings, even if the range of each signal on the data acquisition unit (NI) was set to ± 10 Volts (single-ended), the signal recorded from the analog output of the QZFM electronics module is always cut off in the range of ± 5 Volts (in any variant of gain) or  ± 5 nT (with gain 0.33). (example pic.1)

It can be assumed that the built-in digital-to-analogue converter, which gives a signal to the analog output inside the el.module, is limited to the range of ± 5 Volts. But if we check the digital recording of the signal made by the el.module (with QZFM UI), then we will not see such oversaturation when the signal goes beyond the range of ± 5 nT (with gain 0.33).

Question: If all of the above is true, is it possible to somehow change the range of the built-in digital-to-analog converter inside the el.module?

Thank you!

[James Osborne]

Dear Oleg,

That is correct, the range of the QZFM analog output is ±5 V which corresponds to a magnetic field output of about ±5 nT in 0.33x gain mode. There is an additional 0.1x gain mode that is available for QZFMs with more recent firmware. To see if the command is available, reboot the sensors then send command 30 and check if the response is "Output Gain 0.1x". This will increase the range of the analog output however it is important to note that the sensor output is significantly non-linear outside of ±5 nT, but this will help the issue of saturation. If you require a firmware update to access this command please send a email to in...@quspin.com with a request.  

Here is a graph for reference showing sensor response vs applied magnetic field from our website:

Best regards,

James