Paul, Remember the HP 412? It used incandescent bulbs, a spinning disc, and a syncronous motor. I actually still use two of these, and the bulbs are the only fault.
Best, Will *********** REPLY SEPARATOR *********** On 6/14/2011 at 10:21 PM paul swed wrote: >Though its a bit off topic >Ran into this chopper issue also on a HP410. I replaced the thing with a >modern chopper amp. I think an LTC. This was quite a few years ago (10 plus >easily) and it works very well. Still does actually. It did take a bit of >rework to get things back in balance correctly. > >On Tue, Jun 14, 2011 at 10:14 PM, J. Forster <j...@quik.com> wrote: > >> The reason I asked is that most microvolt bridges use choppers and have BP >> filters at the chopper frequency, so noise is largely uncorrelated. >> >> On the neon photochoppers, it has been discussed at length several times >> on the HP-Agilent Yahyoo Group. A similar thing is used in the 410C. There >> are apparently issues with the CdS cells. >> >> Best, >> >> -John >> >> =============== >> >> >> > John, >> > >> > No, it's DC. I'm trying to meet the original specs of the batteries in >> not >> > only voltage/current, but cleanliness of the current. >> > >> > Now inside the Fluke 844, it has a chopper, and it uses an AC power >> supply >> > internally to feed its circuitry. The Vishays bridge uses the batteries >> > voltage, and one small AC power supply to run the digital portion of the >> > bridge for the PPM readout. The bridge itself is half analog and half >> > digital. The analog for the measurement, and the digital for the PPM >> > difference. >> > >> > By the way, has anyone ever converted a neon NE-3 driven chopper to using >> > LED's? The bulbs have a sqaure wave coming into them of around 100-200 Hz >> > if I recall. >> > >> > Thanks, >> > >> > Will >> > >> > *********** REPLY SEPARATOR *********** >> > >> > On 6/14/2011 at 6:50 PM J. Forster wrote: >> > >> >>Is the bridge excitation AC or DC. If it's AC, you may not even need >> >>low-noise power supplies. >> >> >> >>-John >> >> >> >>============== >> >> >> >> >> >> >> >>> Hi Will, >> >>> >> >>> You could consider building your own power supply system for the >> >>> replacement of >> >>> the batteries. Use a separate power transformer which, I suspect, >> >>> would >> >>> be small >> >>> as the current requirements would be low for driving a bridge circuit. >> >>> >> >>> The main company to look toward for high quality, low noise regulators >> > is >> >>> Linear >> >>> Technology. Here is a candidate part to look at : >> >>> http://www.linear.com/product/LT3082 >> >>> >> >>> This is the lowest noise (33uv/10Hz to 100KHz) low dropout regulator >> > that >> >>> can >> >>> handle regulating 24 volts and is adjustable, meaning use can use this >> >>> part for >> >>> all three voltages (i.e., three regulators). You will have to decide >> >>> if >> >>> it noise >> >>> specs are suitable for your needs. Keep in mind that battery noise is >> >>> typically >> >>> random whereas the noise out of a regulated system tends to be >> >>> constant. >> >>> >> >>> If you really think you need lower noise then you could consider an >> > LT1000 >> >>> shunt >> >>> reference. Typically the circuit designs for LT1000 type devices are >> >>> as >> >>> references and lack current capability above about 10 milliamps. >> >>> Adding >> >>> additional current circuitry would add more noise. See: >> >>> >> >>> http://www.linear.com/product/LTZ1000 >> >>> >> >>> >> >>> Bill....WB6BNQ >> >>> >> >>> >> >>> Will Matney wrote: >> >>> >> >>>> Hello, >> >>>> >> >>>> I am in need of a very clean 24 Vdc power source, to replace some old >> >>>> mercury cell batteries with. What would a good low noise, clean, power >> >>>> supply be in your recommendations? I thought of using two 12 Vdc >> >>>> lead-acid >> >>>> batteries in series, and making a charging circuit with regulators, >> >>>> but >> >>>> I >> >>>> am hoping to purchase a good used supply off ebay, etc. The old >> >>>> circuit >> >>>> used two 12 Vdc snap terminal mercury batteries in series, for 24 Vdc, >> >>>> along with a 7 Vdc mercury cell, and two plain AA carbon 1.5 Vdc >> >>>> batteries >> >>>> in series for 3 volts. Any help and or ideas would be appreciated. >> >>>> >> >>>> Thanks >> >>>> >> >>>> Will >> >>>> >> >>>> _______________________________________________ >> >>>> time-nuts mailing list -- time-nuts@febo.com >> >>>> To unsubscribe, go to >> >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> >>>> and follow the instructions there. >> >>> >> >>> >> >>> _______________________________________________ >> >>> time-nuts mailing list -- time-nuts@febo.com >> >>> To unsubscribe, go to >> >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> >>> and follow the instructions there. >> >>> >> >>> >> >> >> >> >> >> >> >>_______________________________________________ >> >>time-nuts mailing list -- time-nuts@febo.com >> >>To unsubscribe, go to >> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> >>and follow the instructions there. >> >> >> >>__________ Information from ESET Smart Security, version of virus >> > signature database 5851 (20110206) __________ >> >> >> >>The message was checked by ESET Smart Security. >> >> >> >>http://www.eset.com >> > >> > >> > >> > >> > _______________________________________________ >> > time-nuts mailing list -- time-nuts@febo.com >> > To unsubscribe, go to >> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > and follow the instructions there. >> > >> > >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >_______________________________________________ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. > >__________ Information from ESET Smart Security, version of virus signature database 5851 (20110206) __________ > >The message was checked by ESET Smart Security. > >http://www.eset.com _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.