Re: [volt-nuts] Matched resistors
Andreas, Thanks for the information. Do you have the drift chart, etc. posted anywhere? that would be very interesting reading. Thanks, Randy On Fri, Jul 18, 2014 at 10:11 PM, Andreas Jahn andreas_-_j...@t-online.de wrote: Hello Randy, I think the only difference is in oscillator section (and thus power consumption) and of cause the TSSOP-package. The LTC1043 is easily available from stock e.g. from digikey. The LTC6943 is more difficult to get. Within the Keithley 2002 LTC1043 is used. http://www.eevblog.com/forum/testgear/keithley-2002-8-5- digit-dmm-review-and-teardown/ http://dev.xdevs.com/projects/kei2002/repository/entry/ photos/K1/small/K2002_1-2251.jpg I have added a drift chart with longterm drift data. Note: the drift is for the whole measurement arrangement. It consists of 3 7V references (2 LTZ1000A and 1 LM399) measured via a LTC1043 divider with a 24 bit LTC2400 ADC with temperature compensated voltage reference AD586LQ. So most of the drift is related to the AD586LQ reference. (X-axis is in days, Y-axis in ppm) I get around 2 ppm drift for the LTZ1000A over 1 year which I guess is mostly humidity related from the ADC printed cirquit board + AD586 reference drift and usually below 0.25 ppm standard deviation over 1000 hours. (42 days). All at unstabilized room temperature. I guess with resistors you will need ovenized temperature stabilisation to achieve this. with best regards Andreas Am 19.07.2014 05:57, schrieb Randy Evans: Andreas, That is good information, I appreciate it. I have contacted LT application support but they have yet to get back to me on my questions except they did recommend to use the LTC6943 instead of the LTC1043. Later generation I guess. I think i am going to try both the LTC6943 and the LT5400 resistor array and characterize them. The LT5400 matching ratio looks pretty good over temp (0.2ppm/C) but the absolute resistor change over temp is -10 to +25 ppm/C, a little larger than I would like for the circuit I am using. Randy On Thu, Jul 17, 2014 at 10:37 PM, Andreas Jahn andreas_-_j...@t-online.de wrote: Hello Randy, I am using the LTC1043 in 1/2 VIN or 1/3 VIN configuration. A matching of the caps is not necessary. In the 1/2 VIN or 1/3 VIN configuration a matching would give the advantage that the settling time of the cirquit is reduced. But in 2* VIN or inverting configuration a matching gives no advantage. So perhaps it is better to put a 1/2 VIN divider into a feedback loop. The most important point: you will need a low leakage buffer amplifier at the output. The caps should be low leakage foil capacitors. (polypropylene would be best). The ESR is negligible against the switch resistance of around 1000 Ohms And dielectric absorption would also affect only settling time. In 1/2 VIN configuration I am using cheap small mylar capacitors (WIMA MKS02) (isolation time constant is given only with 1250 sec (3000 sec typ)). Buffer amplifier is a LTC1050. The circuit is very stable over temperature (10 - 40 deg C). The absolute amplification error is usually some ppm lower than exact 2:1 value. (depends somewhat on the pinning which is used so I am not shure wether the pins are mixed up regarding the charge compensation) So I dont know wether the ±1 ppm is more a stability figure than a absolute value. Even polypropylene capacitors do not change the amplification error. With best regards Andreas Am 17.07.2014 17:26, schrieb Randy Evans: Frank, The high cost is my concern, although high performance demands high price typically. I am trying to double the voltage reference from either an LM399 or LTZ1000, hence the need for precision matched resistors for a x2 non-inverting amplifier (using a LT1151 precision op amp). An alternative I am investigating is using the LTC1043 in a voltage doubling circuit as shown in Linear Technology app note AN 42, page 6, Figure 16. It states that Vout = 2xVin ± 5 ppm. I am less concerned about the absolute accuracy than I am about the long term stability. I assume that a high quality capacitor is required (low leakage, low ESR, low dielectric absorbtion, etc.) but the circuit does not appear to be dependent on the absolute value of the capacitors. I'm not sure if the two 1uF caps need to be matched. If they do then that would be a show stopper. Does anyone have any experience using the LTC1043 in such a circuit? Thanks, Randy ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow the instructions there. ___
Re: [volt-nuts] Matched resistors
Hello Randy, some information you will get on eevblog. (its much easier to post (larger) pictures there). Namely within the LTZ1000, LM399 and T.C. Measurements threads: http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/ http://www.eevblog.com/forum/projects/lm399-based-10-v-reference/ http://www.eevblog.com/forum/projects/t-c-measurements-on-precision-resistors/ http://www.eevblog.com/forum/projects/oshw-24bit-adc-measurement-system-for-voltage-references/ http://www.eevblog.com/forum/projects/building-a-7-decade-voltage-calibrator/ http://www.eevblog.com/forum/projects/ppmgeek!-5-5-digit-dvm-volt-ref-cal-%28for-arduino-or-any-uc-w-spi%29/msg296127/#msg296127 With best regards Andreas Am 19.07.2014 16:33, schrieb Randy Evans: Andreas, Thanks for the information. Do you have the drift chart, etc. posted anywhere? that would be very interesting reading. Thanks, Randy On Fri, Jul 18, 2014 at 10:11 PM, Andreas Jahn andreas_-_j...@t-online.de wrote: Hello Randy, I think the only difference is in oscillator section (and thus power consumption) and of cause the TSSOP-package. The LTC1043 is easily available from stock e.g. from digikey. The LTC6943 is more difficult to get. Within the Keithley 2002 LTC1043 is used. http://www.eevblog.com/forum/testgear/keithley-2002-8-5- digit-dmm-review-and-teardown/ http://dev.xdevs.com/projects/kei2002/repository/entry/ photos/K1/small/K2002_1-2251.jpg I have added a drift chart with longterm drift data. Note: the drift is for the whole measurement arrangement. It consists of 3 7V references (2 LTZ1000A and 1 LM399) measured via a LTC1043 divider with a 24 bit LTC2400 ADC with temperature compensated voltage reference AD586LQ. So most of the drift is related to the AD586LQ reference. (X-axis is in days, Y-axis in ppm) I get around 2 ppm drift for the LTZ1000A over 1 year which I guess is mostly humidity related from the ADC printed cirquit board + AD586 reference drift and usually below 0.25 ppm standard deviation over 1000 hours. (42 days). All at unstabilized room temperature. I guess with resistors you will need ovenized temperature stabilisation to achieve this. with best regards Andreas Am 19.07.2014 05:57, schrieb Randy Evans: Andreas, That is good information, I appreciate it. I have contacted LT application support but they have yet to get back to me on my questions except they did recommend to use the LTC6943 instead of the LTC1043. Later generation I guess. I think i am going to try both the LTC6943 and the LT5400 resistor array and characterize them. The LT5400 matching ratio looks pretty good over temp (0.2ppm/C) but the absolute resistor change over temp is -10 to +25 ppm/C, a little larger than I would like for the circuit I am using. Randy On Thu, Jul 17, 2014 at 10:37 PM, Andreas Jahn andreas_-_j...@t-online.de wrote: Hello Randy, I am using the LTC1043 in 1/2 VIN or 1/3 VIN configuration. A matching of the caps is not necessary. In the 1/2 VIN or 1/3 VIN configuration a matching would give the advantage that the settling time of the cirquit is reduced. But in 2* VIN or inverting configuration a matching gives no advantage. So perhaps it is better to put a 1/2 VIN divider into a feedback loop. The most important point: you will need a low leakage buffer amplifier at the output. The caps should be low leakage foil capacitors. (polypropylene would be best). The ESR is negligible against the switch resistance of around 1000 Ohms And dielectric absorption would also affect only settling time. In 1/2 VIN configuration I am using cheap small mylar capacitors (WIMA MKS02) (isolation time constant is given only with 1250 sec (3000 sec typ)). Buffer amplifier is a LTC1050. The circuit is very stable over temperature (10 - 40 deg C). The absolute amplification error is usually some ppm lower than exact 2:1 value. (depends somewhat on the pinning which is used so I am not shure wether the pins are mixed up regarding the charge compensation) So I dont know wether the ±1 ppm is more a stability figure than a absolute value. Even polypropylene capacitors do not change the amplification error. With best regards Andreas Am 17.07.2014 17:26, schrieb Randy Evans: Frank, The high cost is my concern, although high performance demands high price typically. I am trying to double the voltage reference from either an LM399 or LTZ1000, hence the need for precision matched resistors for a x2 non-inverting amplifier (using a LT1151 precision op amp). An alternative I am investigating is using the LTC1043 in a voltage doubling circuit as shown in Linear Technology app note AN 42, page 6, Figure 16. It states that Vout = 2xVin ± 5 ppm. I am less concerned about the absolute accuracy than I am about the long term stability. I assume that a high quality capacitor is required (low leakage, low ESR, low dielectric absorbtion, etc.) but the circuit does not appear to be dependent on the absolute value of the
Re: [volt-nuts] Desperately seeking OPTION 10 for Datron 4708
Thank you all for the responses and information. The amount of conflicting information i have gotten so far from other experts is truly astounding. Some say that the AC only option 20 30 Datron 4708 does not have resistance, others say it does. The manual doesn't enlighten any further. I have also heard that the 4000/4000A boards do not work in the 47XX series. I have gone ahead and purchased a Datron 4000 (option 90), to complement my Datron 4708 (options 20, 30,80, 90). I am hoping this combination will give me DC V+I, AC V+I, and resistance at 8.5 digit accuracies, that i can further characterize with my Agilent 3458A (NIST traceable cal). Does anyone have a complete manual for the 4000/4000A? Either electronic or hard copy, thank you! On Wed, Jul 16, 2014 at 8:48 AM, Chris caal...@gmail.com wrote: Thank you for the bad news :( I am starting to come to terms with the difficulty of finding this option. I have recently discovered that option 10 from the 4700, 4705, and 4707 would also work. Not sure if this makes it any easier. Also my unit has a sticker on the front indicating ac voltage and current only... But lists options 20,30,80,90 on the backside label. Will my unit have resistance functionality? I am hearing a lot of conflicting information. Not sure if I am replying to emails correctly. (New to volt nuts) On Jul 12, 2014 6:03 PM, Chris caal...@gmail.com wrote: Nobody has access to spare Datron 4708 stuff? I am willing to pay international shipping etc... whatever it takes! Thank you On Thu, Jul 10, 2014 at 2:09 PM, Chris caal...@gmail.com wrote: I am looking to purchase OPTION 10 slide in board for the Datron 4708 Multifunction Calibrator. If anybody has a parted out unit and can sell me just the option 10 board i would appreciate it dearly! Thank you for considering! Chris ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
