EDC VS330 - Page 1
Forum section: electronics / testgear

author: mojoe
author_rank: Frequent Contributor
timestamp: August 06, 2013, 01:54:32 am
content: After seeing Dave's video on the EDC MV106, I bought an EDC VS330, which goes up to 300 VDC. The problem is, I can't find a manual. I contacted Krohn-Hite and they say the manual is no longer available. I don't need a manual for operation, as it is pretty straight forward. I would like the schematics, however.Does anyone have a manual for this model? A PDF is preferred, but a paper copy, or even a loaner that I could scan would be greatly appreciated. Feel free to PM me if you have something.Joe

author: mojoe
author_rank: Frequent Contributor
timestamp: August 09, 2013, 01:18:25 pm
content: Although I'm still looking for a manual, I have been able to mostly confirm that this unit is working well. My HP 3478A reads too high when hooked up to the VS330. I borrowed four other meters to compare (one 4.5 digit, two 5.5 digit and one 6.5 digit). All of these meters read either dead on, or +/- 1 count on all ranges. I don't know anyone with a higher resolution, calibrated DMM.Joe

author: saturation
author_rank: Super Contributor
timestamp: August 09, 2013, 07:24:29 pm
content: Hi Mojoe, I follow your posts on volt-nuts. Overall, the EDC VS330 based on the specs posted here:http://www.ebay.com/itm/Electronic-Development-Corporation-EDC-VS330-VOLTAGE-STANDARD-/161069656213?nma=true&si=k5pgLH0YqLIN8GQi3d3eNVOCt4k%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557are superior to your 3478A which is 60 ppm in DC, 3x more than the 20 ppm of your EDC.http://electronicsandbooks.com/eab1/kb/k0zfca/r0zfca01q.htmSo overtime, assuming both began calibrated, the HP would drift far more than the EDC if left untouched for the same amount of time.IIRC When Dave posted his review of the EDC MV106 his unit was in cal; mine was not which I bought roughly at the same time as his review, YMMV with how its used or ab-used.Since you've compared its readout to a cal'd 6.5 digit DMM, and its spot on, its more certain the 3478a is out of cal not the EDC.Getting a more precise DMM capable of 7.5 or 8.5 digits to check the EDC isn't necessary because the accuracy of the EDC is 20 ppm [ and that's already best case];, the LSD on each EDC range is inaccurate except for making short term precision comparisons. For example, at 300V range, 20 ppm means its varies to 6mV/300V, even if you can adjust the EDC down to 900uV [ its specs and my experience with other EDC units does show the short term 1 hr stability of 5ppm is realizable, but its still limited to 1.5mV/300VDC range.]Enjoy, its a great unit and fairly uncommon, thus the difficulty finding the manual. Key to checking it has been your ability to compare its output against a cal'd 6.5 DMM.I would get a copy of the MV106 manual and compare your PCB against the MV106 since EDC often made the calibrators the same way and just added daughter boards or changed resistor values to turn them into this-and-that-model, among a line of analog calibrator models.DC REFERENCE VOLTAGE STANDARD AND CALIBRATOR 300MV TO 300VThe Model 330 is a high accuracy, highly transportable D.C. Voltage Standard and Calibrator. It may also be used as an ultra stable source. Designed for application above 100 Vdc but not requiring the availability of 1000 V with the attendant hazards.FEATURES:Outputs: 0.1 uV to 300 VdcCurrent: up to 100 mAAccuracy: 0.002%Solid State hybrid design4 terminal remote sensingWarm-up in less than 30 secondsSPECIFICATIONS:Output: 300V Range: ± 311.111,0 Vdc30V Range: ± 31.111,10 Vdc3V Range: ± 3.111,110 Vdc300mV Range: ± 311.111,0 VdcReselution: 300V Range: 100 uV30V Range: 10 uV3V Range: 1 uV300mV Range: 0.1 uVRipple & Noise: Rms. 0.1 Hz to 100 kHz bandpass (0.001% of range + 5uV)Output Current: With 4-terminal remote sensing, and current limit control.300V, 30V, 3V, Ranges: 100mAExcept above 100V: 25mA300mV Range: into high impedance loads (>200k?)Load Regulation: *(non-additive): <50mA = ±(0.0015% + 25uV)No load to full load: >50mA = ±(0.005% + 25uV)Line Regulation: *(non-additive): ±0.0005% of setting + 25uV for a 10% line change.Output Impedance: 300V, 30V, 3V Ranges: 0.02?300mV Range: 20? (constant)Output Accuracy (2 methods):Calibration Accuracy: ±(0.002% of setting + 0.0005% of range 5uV)The Calibration Accuracy is at Standard Reference Conditions at time of calibration.Nominal calibration temperature of 23ºC ± 1ºC at 70% Relative Humidity.Nominal line voltage 117 Vac at constant external load.Limit of Error (worst case) Accuracy: ±(0.003% of setting + 0.001% of range + 5uV)*The Limit of Error Accuracy includes peripheral, additive specifications (i.e., Error for line and load changes, ambient operating temperature changes and stability). Calibration cycle: One Year.Stability: *(non-additive) 1 hr. ±.0005%8 hr. ±.001%1 yr. ±.005%Quote from: mojoe on August 09, 2013, 01:18:25 pm

author: mojoe
author_rank: Frequent Contributor
timestamp: August 10, 2013, 01:32:46 am
content: Saturation,Thanks for the feedback. None of the DMMs that I borrowed were in cal. The fact that all of them agree tells me that the VS330 is at least fairly accurate. I'm still looking around the local area to see who might have a 7.5 digit DMM, preferably in cal.I do tend to like my test equipment as accurate as possible, even if I don't need it that accurate. It must be a personallity flawFrequency is so easy for the hobbyist. A GPSDO is very affordable (had one for several years). Those other quantities are more expensive.What started me down this road was the necessity of an accurate DMM to use when servicing older test equipment. I usually can't afford the cost of high-end new gear, so like many others, I search out the 10-30 year old stuff that used to cost many thousands. You may think that being several millivolts off is no big deal, but with some of that older gear, the service manuals may call for better accuracy.It was after I adjusted such a piece of equipment that I began to question my HP 3478A. I bought a Maxim DC reference chip, built a circuit and it confirmed my suspicion. However, I couldn't use that reference to calibrate the HP, as it needs voltages at each of the full scale values. After seeing Dave's video, I picked up the VS330. It goes up to 300+ VDC, which is perfect for calibrating the HP 3478A. Thus, the need to see how accurate the VS330 is (and on and on it goes...).With a known accurate DC reference, I can buy some precision resistors and make a current reference. AC is a bit harder, but I have some possibilities in the works.As for the manual, I would still like to find one. I like having service manuals, or at least schematics for my stuff, just in case.Joe

author: saturation
author_rank: Super Contributor
timestamp: August 10, 2013, 11:54:37 am
content: Hi Joe,If you cannot borrow one to compare, in the USA one option other than a cal lab is rent a 7.5 digit DMM for $90-$150/mo, delivered. A benefit over sending it to a cal lab is being able to strictly compare every range and since rentals are often monthly, it allows to you match all your ranges dead on over longer periods of time until you are satistfied. A cal lab may spend only minutes and maybe an hour total time calibrating your device and won't account for small drifts that happen after you adjust a pot that hasn't been turned in decades. Often what looked good in a cal lab won't be as good when you receive the device many days later, shocked by shipping handling and the temperature changes of travel.7.5 digits is preferred to check the VS330 as the reference is good to 6.5 digits, for a TUR of 10:1.https://www.metrictest.com/product_info.jsp?mfgmdl=KEI%202001&rtab=bisI agree with your sentiments exactly, see bold items, I put together such a lab searching for metrology gear of yester-year over 3+ years. You needn't build your own, just wait for one to appear on eBay, as you did with the VS330.Your 3478a is a good bench meter, but its meant as a service meter not a high accuracy meter; I'd recommend at least the 3456a or 3457a if you're a stickler for accuracy!Quote from: mojoe on August 10, 2013, 01:32:46 am

author: mojoe
author_rank: Frequent Contributor
timestamp: August 10, 2013, 06:49:46 pm
content: Saturation,I hadn't thought of renting. That is a good idea. I had also been thinking about trying to find a better DMM on ebay or elsewhere. Thanks again.BTW, that long thread about the LTZ1000 has been very informative.Joe

author: radioFlash
author_rank: Regular Contributor
timestamp: April 05, 2015, 03:15:07 pm
content: Someone has uploaded the manual to the KO4BB manuals site:http://www.ko4bb.com/manuals/download.php?file=06_Misc_Test_Equipment/Krohn-Hite_VS330_DC_Voltage_Standard_Operator_Manual-1979_and_Before.pdf

author: mojoe
author_rank: Frequent Contributor
timestamp: April 06, 2015, 09:54:46 pm
content: Thanks for posting the link, but I was the one who uploaded the manual.Khron-Hite originally told me that a manual was no longer available. Months later, they sent me a PDF. Seems they found a manual afterall. I asked them if it was OK to upload it to KO5BB and never got a reply, so I uploaded it.

author: radioFlash
author_rank: Regular Contributor
timestamp: April 07, 2015, 12:00:36 am
content: Quote from: mojoe on April 06, 2015, 09:54:46 pmI thought I'd post it here since the thread was the first hit that came up in Google--thanks for uploading it!