| Products > Test Equipment |
| R&S HMP4040 voltage spike at PSU turn-off |
| << < (4/12) > >> |
| electr_peter:
What are output impedances measured with DMM on PSU turned-off? With sense terminal unconnected: * between output terminals - 10kOhm * between sense terminals - 12.9kOhm * between output- and sense- terminals - 1.47kOhm * between output+ and sense+ terminals - 1.47kOhm * between output+ and sense- terminals - 11.5kOhm * between output- and sense+ terminals - 11.5kOhmWith sense terminal shorted to output (+/+ & -/-): * between output terminals - 10kOhm |
| mahi:
electr_peter: When shorting the sense lines to the outputs, the ramp-up voltage increases to 1.6 V maximum (instead of 1 V) on my HMP4040. This does indeed suggest that the sense circuitry is to blame for this behavior. Still, the voltages on my unit are much lower than on yours. There is no change to Gough Lui's scenario with the sense lines shorted to the outputs. The resistances between the output terminals on my HMP4040 are quite different from yours: With sense terminal unconnected: between output terminals - 1.87 kOhm between sense terminals - 4.82 kOhm between output- and sense- terminals - 1.47 kOhm (same as yours) between output+ and sense+ terminals - 1.47 kOhm (same as yours) between output+ and sense- terminals - 3.34 kOhm between output- and sense+ terminals - 3.34 kOhm With sense terminal shorted to output (+/+ & -/-): between output terminals - 1.87 kOhm All outputs show identical values within tens of ohms from each other. |
| electr_peter:
@mahi, resistances are quite different. There could be some error due to diodes turning on in circuitry and different DMM effect, but that would not account for such big differences. Lower impedance will dampen voltage ramp effect, so there is explanation why yours HMP is more tame. This data confirms that HMP4040 has different HW versions for channel boards. R&S probably find out this issue and did a HW revision at some point. Do you recall manufacture/sale date of PSU? Mine is from 2015-2016 or earlier. |
| electr_peter:
Based on measurements and general PSU configuration I estimated rough schematic of sense circuitry. There are three main resistance elements and two voltage cut-off points (relay for main output and transistor for sense circuit). During turn-off sense transistor becomes activated and leaks voltage. It is clear that different HW versions have different resistive values. I will try recreating impedances similar to @mahi PSU and see how it compares in terms of turn-off spike. |
| mahi:
electr_peter: I can't find any date markings on the outside, but I purchased my unit in spring 2018. Thus it was probably made in 2017-2018. By the way, your diagram can't be right. You have a direct connection between the sense circuit and the outputs. In your diagram R+ and R- serve no (useful) purpose. The diagram below (taken from the user manual) is incomplete, but it shows the link between the outputs and sense circuitry. |
| Navigation |
| Message Index |
| Next page |
| Previous page |