I forgot to add that noise on the bridge excitation should not matter much when the bridge is at null, as the differential mode voltage is zero.
-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.