Simple divider jpg
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PM me if you are interested in the PCBs, think I still have a couple. The Analog Devices ADR4550 I have in the shown PCB is really good, been very stable over the past couple weeks, same goes for the AC waveform (250Hz form 4.096MHz crystal). The reference voltage supports many of the popular ref sources that use a SOIC footprint, including trim components. Not intended to be standards, but hard to beat for ease of use!! They also support many different components, so for the resistors you can mix and match with 0603, 0805, 1206, 1210 or leaded devices.
I have a precision based LTZ1000 and LM399 design waiting for these connectors!! These are so easy and convenient to use, I just plug and swap between the two 34401A and 34465A DVMs to check on how they compare. Sorry for the late reply, I missed this somehow, senior moment The connectors plugs are from eBay, but it took me a few sets purchased, over 4 months to finally get what I liked, then the eBay supplier shipped the wrong jacks.so back to square one! I'm waiting on another set of jacks, and if they are right then I'll try another reordereding of the plugs. Of course this isn't NIST certified, nor even ultra-precision, but adequate for my needs Here's some images of the resistor PCBs. All readings are very stable on the 34401As or 34465A after a time to settle in to DVM input temperature. The Keysight 34465 has a nice feature of directly converting 5K and 10K thermistors to temperature, also the trend chart is really nice for observing readings of voltage, resistance and temperature. All these used gold plated Banana plugs for direct DVM mounting, very convenient With a nominal room temperature of ~77F they measured about ~82F or ~28C, so the inputs to the DVMs seems to be about ~5F warmer than ambient. The Calibrator used a 1206 10K 0.1% 10ppm resistor, a 10K 0603 1% thermistor, a 4.096MHz 20ppm Crystal and a Analog Devices ADR4550 5 volt reference. Used a hermetic 10K 1% leaded thermistor. I built the 1st of the Resistor PCBs with 5ppm resistors, 100 ohm 0.05% 1206, 1K Vishay 0.1%, 10K 0.1% and 100K 0.1%. 6) Standard Power 12V connector and also 2 pin battery connector, both reverse protected. Separate pins which can be read by DVM or another meter. 5) 3 Thermistors types to read PCB temperature, leaded, 0603 or 0805. Has discrete output buffer for lower impedance. Jumper enables AC waveform and another jumper selects frequency from 14 stage counter (CD4060). Supports various crystals & frequencies, HC49 or leaded type. 4) AC Voltage reference, creates accurate 50% duty cycle square waveform of Vref, thus rms value is Vref/2. Layout supports various trim techniques for various references, and includes trim pot. Pin 2 Vcc in, Pin 4 And, Pin 6 Vout, Pin 5 Trim. 3) DC Voltage reference, can be various voltages (2.5, 5, 10 volts with different pre-regulator) and has somewhat standard "footprint" of SOIC 8 pin. 2) Single resistor position, can be Leaded type, 0603, 0805 or 1206, or various combinations. B) "On-DVM" Calibrator PCB, 1) Functions selectable by jumpers. 5) Rotated CCW 90 degrees becomes and good zero Volt & Ohm (2 or 4 wire) reference. 4) Directly connects to DVM by Banana plugs, no leads required. 3) 3 Thermistors types to read PCB temperature, leaded, 0603 or 0805. 2) Each resistor can be a Leaded type, 0603 type, 0805 type or 1206 type, or various combinations (for adjusting value).
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1) 4 resistor positions selectable by jumpers for 4 wire measurements. Anyway, long story short a few custom PCBs were designed and fabricated. Instead of sending everything out for calibration, decided to get a new Keysight 34465A DVM and use this to help calibrate/check the other instruments. Earlier had repaired a couple Tek 2465 scopes, so beginnings of a new to me lab at home While revisiting and old unique voltage divider circuit (used a flip-flop) and measuring, the result the two DVM differed by a small amount, then realized I needed something to calibrate these 34401A and the two old Flukes (87 and 77) we had laying around. After retiring last year I purchased an HP34401A off eBay for repair, then repair an Agilent 34401A.