I have an HP 34970A data acquisition / switch unit https://www.keysight.com/en/pd-1000001313%3Aepsg%3Apro-pn-34970A/data-acquisition-data-logger-switch-unit It is essentially a 6.5 digit DVM with plug-in modules that allow one to perform analog measurements, digital I/O, switching etc. I am going to get the mainframe calibrated by Keysight - not all the plug in modules. I read somewhere it is essentially a 34401A multimeter https://www.keysight.com/en/pd-1000001295%3Aepsg%3Apro-pn-34401A/digital-multimeter-6-digit which makes sense. The design of the unit is poor in that the S/N is put on the rubber bumpers. They often get charged. I have no idea of the S/N. One of the service notes refers to a possible unstable resistor in a range of S/Ns. I changed that resistor, on the off-chance mine might have been bad. Following changing the resistor I switched the unit on/off periodically for a few weeks to try to relieve any stress following soldering the resistor in. I am wondering if it is best to power cycle or leave the unit one for a few days before sending for calibration. Or should I not bother given it is only 6.5 digits? I don’t use the unit much, and when I do I am not going to leave it running more than an hour or so before taking measurements. Dave -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@kirkbymicrowave.co.uk https://www.kirkbymicrowave.co.uk/ Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom

We kept all our HP 3458As running all the time. If you turn them off for a few months the stability will not be as good as if it was on all the time. On Mon, May 11, 2020 at 5:39 PM Dr. David Kirkby < drkirkby@kirkbymicrowave.co.uk> wrote: > I have an HP 34970A data acquisition / switch unit > > > https://www.keysight.com/en/pd-1000001313%3Aepsg%3Apro-pn-34970A/data-acquisition-data-logger-switch-unit > > It is essentially a 6.5 digit DVM with plug-in modules that allow one to > perform analog measurements, digital I/O, switching etc. I am going to get > the mainframe calibrated by Keysight - not all the plug in modules. I read > somewhere it is essentially a 34401A multimeter > > > https://www.keysight.com/en/pd-1000001295%3Aepsg%3Apro-pn-34401A/digital-multimeter-6-digit > > which makes sense. > > The design of the unit is poor in that the S/N is put on the rubber > bumpers. They often get charged. I have no idea of the S/N. > > One of the service notes refers to a possible unstable resistor in a range > of S/Ns. I changed that resistor, on the off-chance mine might have been > bad. Following changing the resistor I switched the unit on/off > periodically for a few weeks to try to relieve any stress following > soldering the resistor in. > > I am wondering if it is best to power cycle or leave the unit one for a few > days before sending for calibration. Or should I not bother given it is > only 6.5 digits? > > I don’t use the unit much, and when I do I am not going to leave it running > more than an hour or so before taking measurements. > > Dave > -- > Dr. David Kirkby, > Kirkby Microwave Ltd, > drkirkby@kirkbymicrowave.co.uk > https://www.kirkbymicrowave.co.uk/ > Telephone 01621-680100./ +44 1621 680100 > > Registered in England & Wales, company number 08914892. > Registered office: > Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United > Kingdom > _______________________________________________ > volt-nuts mailing list -- volt-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com > and follow the instructions there. > -- *John Phillips*