Frequently Asked Questions
Design
Q: Is it really such a good design?
A: Yes it is. You can read this in HPM7177 evaluation report.
Q: Can I get the schematics?
A: Yes, you can. The design is licenced under the CERN Open Hardware Licence and therefore anyone should be able to see the sources, study it, modify it and share it. In addition, if modifications are made and distributed, it must be under the same licence conditions – this is the ‘persistent’ nature of the licence, which ensures that the whole community will continue benefiting from improvements, in the sense that everyone will in turn be able to make modifications to these improvements.
You can find the schematics and other production documentation under Project Information.
Q: Is it possible to operate the device without the built-in Peltier temperature stabilization?
A: Yes. However, the performance will be degraded in terms of temperature drift. Without stabilization, gain drift will be on the order of 1 ppm/°C, and offset drift will be several times lower. With stabilization, the drift is much lower - on the order of 0.03 ppm/°C (gain) and <0.02 ppm/°C (offset).
Q: Is it possible to operate at other sampling rates (not 10 kSamples/s)?
A: In principle, yes. But it would require changes in the FPGA code and firmware.
Readout
Q: Can I read out the data over USB?
A: Yes, it is possible. In our systems the data will always be streamed over the plastic optical fibre, but the device can operate in standalone mode using the isolated USB interface (in HPM7177 V2).
Q: How can I read the data from the plastic optical fibre?
A: In our test setup we have built a POF to differential LVDS converter card, that fits a NI PXIe system. In the final application the ADC will send data to a controller over the POF interface and will receive synchronization pulses over it. It is straightforward to build a POF interface board (see Sheet #3 of the Mainboard schematic )
08 January 2021