Post by Lake Shore Ryan on Feb 13, 2019 1:19:30 GMT -5
First of all, thank you for purchasing one of new teslameters and probes!
The current implementation of pulse capture is split between two functions of the teslameter.
1. Analog output
The analog out on the back of the unit can be used to view the shape of a pulse using an oscilloscope (or some other high-speed voltage capture device) and then converting to equivalent field values using the process outlined in Section 2.4.5 of the teslameter manual. The teslameter should be placed in high-frequency mode to pause the current spinning function of the unit and give you a nice steady analog out signal. AC mode would not be very useful here given that the current spinning results in a modulated output that would be tricky to interpret.
Since there is only one analog out port, you'll have to configure analog out to respond to the axis that is aligned perpendicularly to the direction of the pulse. Section 3.5.4 of the manual shows this step. For example, if you were to place the probe down the axis of a solenoid, you would want to select the Z-axis as it is the sensor that will pick up fields through the axis of the probe.
The equation quoted in section 2.4.5 will be good for calculating an approximate field values based on measured voltage. It is possible for you to create your own more precise conversion values though, which is where the next point comes in.
2. Peak-to-peak readings
The teslameter samples values very quickly (200,000 times per second) but processes the data heavily before displaying values to the user. Peak-to-peak values in both AC and high-frequency mode report the difference between the highest and lowest field values over a period equal to the averaging window. Therefor it is possible to capture the peak value of a magnet pulse by setting the averaging window to large time interval (10 seconds for example) and expose the probe to a pulse. The highest field value will be captured with a time resolution of 5 μs. This value could be used as a reference point for the peak value of the external voltage capture device. AC mode would be the best choice for measurement accuracy for this task, however it does have some caveats:
Pulse width should not be faster than 10 ms, any faster and the signal will begin to be attenuated, throwing off the measurement
The analog output would not be intelligible, meaning you would have to measure peak value of one pulse in AC mode, then switch to HF mode for the analog output reading for the next pulse and hopefully the two pulses were similar enough for the conversion to be valid.
Otherwise, high-frequency mode would be the best choice as fast pulses would not be attenuated and the analog out voltages could be captured at the same time.
Wow, is it over yet?
I hope this has made some sense and that you're able to apply this in your situation.
We're always on the lookout for ways to improve the usability of the teslameter though, so if you have any feedback or could tell us a little more about how you intend to use the unit, we may make some changes in the future that would make your application easier. Thanks.
Ryan Oliver Product Manager, Sensors and Instruments Lake Shore Cryotronics