How can I convert a frequency to DC voltage with a lab instruments - Page 1
Forum section: electronics / testgear

author: HighVoltage
author_rank: Super Contributor
timestamp: July 22, 2019, 05:20:19 pm
content: Is there alab instrumentthat converts frequency (0 to 50 kHz) to DC voltage (May be 0 to 10V)?I am using a self made simple converter but I need more accuracy and precision and more importantly I need to get this "instrument" officially certified and calibrated.Any suggestions?

author: jpb
author_rank: Super Contributor
timestamp: July 22, 2019, 05:45:24 pm
content: It is probably not suitable and anyway rather over the top, but the Stamford Research SR620 has analogue output meant for XY scopeshttps://www.bellnw.com/manufacturer/SRS/SR620.htmThere may be other similar, somewhat ancient, instruments that have output meant for plotters.

author: mindcrime
author_rank: Unknown
timestamp: July 22, 2019, 06:18:07 pm
content: Quote from: HighVoltage on July 22, 2019, 05:20:19 pmLet me see if I understand this... you want to feed a signal into some device, at a given AC frequency, and get back out a constant DC signal at a voltage that changes to reflect the frequency of the input signal?Edit:Not sure how close this is, but the oldHP 8590 series Spectrum Analyzers, with Option 9, have a feature that might be applicable:QuoteEdit2: never mind, even if that output was what you're looking for, these instruments only go down to 9KHz. :-(

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 22, 2019, 07:34:31 pm
content: I googled "industry class F/V converter" (not sure if this is the correct search therm) and found this:https://www.onosokki.co.jp/English/hp_e/products/keisoku/revo/fv1500.htm

author: BU508A
author_rank: Super Contributor
timestamp: July 22, 2019, 07:51:07 pm
content: How about something like the Advantest R5362B?With the option R13001B you'll have a D/A output from 0 ... +9.999V (see page 4 of the attached pdf)Available here:http://www.rainer-foertig.de/Frequenzzaehler.htmOM:https://www.advantest.com/documents/11348/146687/pdf_mn_ER5361B62B_OPERATING_MANUAL.pdfEdit: TypoEdit 2: added link to operating manual

author: HighVoltage
author_rank: Super Contributor
timestamp: July 22, 2019, 08:23:13 pm
content: Thank you all@jpbInteresting SR620, that I was not aware of. Thanks.@mindcrimeYes, spectrum analyzers are not suitable, I tried that already.@PA0PBZThat might be the correct tool for the job. I will investigate further in to this FV1500.It looks impressive.@BU508AAll counters with analog DC output (For plotters) that I looked at, spread the DC range over the full counter bandwidth range. This Advantest counter may be is different I will take a closer look.Somehow I need to be able to set the DC output references to something like this for example:6 kHz = 0V22 kHz = 10V

author: tautech
author_rank: Super Contributor
timestamp: July 22, 2019, 08:41:15 pm
content: Quote from: HighVoltage on July 22, 2019, 08:23:13 pmLike a VCO in reverse, right ?Interesting.

author: HighVoltage
author_rank: Super Contributor
timestamp: July 22, 2019, 08:45:53 pm
content: Yes, you are right, like a reverse VCO.But in quality of a lab instrument with settable parameters.

author: filssavi
author_rank: Frequent Contributor
timestamp: July 22, 2019, 09:03:19 pm
content: Just out of curiosity, why do you need a f to V converter?I’m sure you are aware it is much simpler to do it in the digital domain either with a simple Schmidt trigger and a counter for simple signals, or in case of complex signals just digitise the whole thing and then find the frequency in DSP?Also if you need the analog signal for interfacing with other vintage/legacy system you could use a microcontroller with integrated DAC and an opamp

author: edavid
author_rank: Super Contributor
timestamp: July 22, 2019, 09:09:38 pm
content: Quote from: HighVoltage on July 22, 2019, 05:20:19 pmSure, just ask your friendly local boatanchor dealer for an HP 5210A:.QuoteThen you'll also need a Tektronix AM501:.QuoteOK, seriously... the second requirement is tough, but how about a TAPR TICC with a little custom code to generate the voltage output?https://tapr.org/kits_ticc.html

author: GerryR
author_rank: Frequent Contributor
timestamp: July 22, 2019, 09:19:03 pm
content: I don't know if building your own instrument is still an option, but one of these modules:https://www.dataq.com/products/di-8b/di-8b-45/di8b45-08.htmlwith a zero and span adjustable output amplifier should get you what you want. (I don't know your input level requirements, though. These are TTL and zero crossing selectable input modules.)

author: nctnico
author_rank: Super Contributor
timestamp: July 22, 2019, 09:43:51 pm
content: How about a frequency counter, an SMU and some software running on -whatever- ? Or wouldn't that meet the response time requirements?

author: David Hess
author_rank: Super Contributor
timestamp: July 23, 2019, 02:25:25 am
content: The Tektronix TVC501 Time-Voltage Converter is another example of that sort of instrument:http://w140.com/tekwiki/wiki/TVC501For continuous measurements, any voltage-to-frequency converter can be used to make a frequency-to-voltage converter by placing it inside the feedback loop of a phase locked loop. But for operation at low frequency, a time-to-voltage converter is more appropriate.

author: graybeard
author_rank: Frequent Contributor
timestamp: July 24, 2019, 05:39:30 pm
content: Try using a pulse generator with a fixed output pulse width just a bit shorter than the period of the highest frequency you want to convert. Trigger the pulse with the frequency reference or signal. The duty cycle will be proportional to frequency. You can then integrate it with an RC filter. You can adjust the the voltage of the top and bottom of the pulse waveform to get the exact voltage range you are looking for.

author: graybeard
author_rank: Frequent Contributor
timestamp: July 24, 2019, 05:54:49 pm
content: If you want a real boat anchor there is always theHP500B frequency meter.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 24, 2019, 07:10:00 pm
content: Damn trashed some industrial din rail modules, exactly like you search, they were in a pcb oven we dismantled at my job, i read their specs up to 100 khz, for +/- 5v input differential or 10v to ground output.Kept them for 2 months before trashing themI cant recall the ic they used, it was a very simple board.Some similarities, it was a green module, i think in the fl228 serieshttps://www.newark.com/c/automation-process-control/signal-conditioning/signal-converters?signal-conditioner-input=frequencyhttps://encore-elec.com/products/frequency-voltage-converters/https://www.phoenixcontact.com/online/portal/ca?uri=pxc-oc-itemdetail:pid=2864082&library=caen&tab=1check the fl228https://www.globalspec.com/ds/683/areaspec/form_factor_din_railhttps://encore-elec.com/model-fl228-frequency-to-voltage-converter/FL228 version 018 can go up to 100 khz, you have one who can go up to 150 khz

author: TimFox
author_rank: Super Contributor
timestamp: July 25, 2019, 08:08:50 pm
content: One of my treasures is a vacuum-tube era General Radio 1142-A “Frequency meter and discriminator” with full-scale frequencies of 150, 1500, 15 k, 150 k, and 1.5 MHz. It is very accurate and linear at the analog voltage output. It has a huge and beautiful front panel meter, whose accuracy is compromised by the use of a temperature-sensitive 1N914 silicon diode to give an expanded scale. The unit uses a charge pump to an averager to produce the output.

author: BU508A
author_rank: Super Contributor
timestamp: July 25, 2019, 09:14:34 pm
content: The ADFV32 from AD can do both: V/F and F/V conversion.Link to the website:https://www.analog.com/en/products/advfc32.html#product-overviewDatasheet direct link:https://www.analog.com/media/en/technical-documentation/data-sheets/ADVFC32.pdf

author: nctnico
author_rank: Super Contributor
timestamp: July 25, 2019, 09:25:26 pm
content: Read the first post carefully: the question is to have the equipment calibrated by a lab. I'm quite sure the OP is more than capable to design a circuit himself but he needs a third party (likely traceable) calibrated solution.

author: BU508A
author_rank: Super Contributor
timestamp: July 25, 2019, 09:32:25 pm
content: Quote from: nctnico on July 25, 2019, 09:25:26 pmYes, I'm aware of this.My purpose was more a general information if somebody else is looking for a V/F and/or F/V converter.

author: HighVoltage
author_rank: Super Contributor
timestamp: July 26, 2019, 10:17:57 am
content: Thank you all for the replies.I have my own F->V circuit for this and it works very well. But the client (Automotive OEM) requires the full chain of test procedure to be calibrated and certified and they do not allow none certified products.One reason to display the voltage instead of frequency is to show the change in frequency on a scope on the time domain.For example:- Start frequency 5 kHz- Stop frequency 29 kHz- Time for the cycle: 10 msAnd many other similar scenarios.Essentially looking at df/dt during the period of 10 ms and see in one picture if it deviates from the set values.The FV-1500 High Speed F/V Converter might be the perfect tool for this.But may be someone here has a better idea of how to show frequency change over time in one picture with all relevant measurements.

author: Henrik_V
author_rank: Regular Contributor
timestamp: July 26, 2019, 12:47:54 pm
content: If you find a Cal-Lab for the F->V converter you have half of the job for your hardware solution... challange is the uncertainty for higher df/dt ...The modern way ... ADC (calibrated and certified) and software.. to test the software you can use the soundcardand switch to a PXI system for the customerA quick good/fail would be a simple correlation ....

author: 2N3055
author_rank: Super Contributor
timestamp: July 26, 2019, 02:36:14 pm
content: Did you try using measurement trend graph on frequency measurement? It works on my Keysight scope.

author: nctnico
author_rank: Super Contributor
timestamp: July 26, 2019, 02:38:24 pm
content: Quote from: HighVoltage on July 26, 2019, 10:17:57 amIf it is just to show on screen as a graph then there is a different solution, The R&S RTM3000 series oscilloscopes have tracking math nowadays. This allows to make a changing frequency to show as a changing math channel. I don't know if the RTB2000 series has similar abilities. If yes then this would be a considerably cheaper option.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 26, 2019, 03:40:10 pm
content: There could also be higher grade frequency counters that alow for a 10 ms or similar gate time and do show statistical values like min, max, average.A analog frequency voltage converter may also have some delay / filtering function and may not respond very fast.There is some chance some DMMs like the DMM7510 could also measure the frequency fast enough and display a curve and statistics.

author: filssavi
author_rank: Frequent Contributor
timestamp: July 26, 2019, 03:59:44 pm
content: Dependong on the required precision you could use a modern(ish) oscilloscope, I’m sure that both lecroy (HDO4000/6000 and 8000 series) and Tektronix (the new 4/5 series) are capable of displaying a measurement’s trend vs time, and also they can do math on the measurement themselves, so you can probably use that and automate it with some sort of pass/fail mask system, your frequencies are slow enough to be easily inside the bandwidth of the most basic model in the seriesIf you need more precision, I’m afraid some sort of software will be almost unavoidable, to make it as simple as possible you could use a calibrated frequency counter, triggered by a calibrated waveform generator, so the post processing Will be very easy, just a division, also calculating error bands and such won’t be hard, with that said If they are adamant that the whole thing must be calibrated end to end I don’t have any other idea, especially since even if you could find some ancient HP/tek bit of gear it will be nigh on impossible to find someone able or willing to do a traceable calibration on the thing

author: Henrik_V
author_rank: Regular Contributor
timestamp: July 29, 2019, 01:18:23 pm
content: Getting a stable analog 'lab-grade' solution (and getting it calibrated) migth be more challenging compared to a ~ 100 kHz ADC (USB/PCI(e?)) (and it's quite common/aka 'cheap' calibration) and a validation of your software.Speed isn't the problem.... the user will need much longer than it will take to compute itI would test it with the soundcard and use LabVIEW .... if you have a hammer ....

author: Henrik_V
author_rank: Regular Contributor
timestamp: July 30, 2019, 12:49:50 pm
content: here is a QD LabVIEW test, I 'rebuild' a F2U converter (measure time between zero crossings ) .. (no noise added ..)I think a traceable ADC board with is hard to beat and more flexible.

author: HighVoltage
author_rank: Super Contributor
timestamp: August 01, 2019, 02:04:12 pm
content: Thank you HenrikThis seems to be a very good idea and easy to implement, but ....I talked to my client and they would not approve, it has to be a certified lab instrument to be accepted.

author: JPortici
author_rank: Super Contributor
timestamp: August 01, 2019, 03:05:11 pm
content: As other suggested, what about using an oscilloscope that can plot math?like any Lecroy (with their OS, not the waveace or the like), any keysight from the 3000T, any Picoscope and, apparently, even the RTM 3000?(Besides, i've been requesting this feature since forever for the siglent 5000X @Performa01 @tautech. Apparently i'm not the only one that plays with MAF sensors -at least, i suppose it's a MAF or a simillar sensor. It' the only thing i can think of that outputs this kind of signal in a car-)

author: nfmax
author_rank: Super Contributor
timestamp: August 01, 2019, 05:01:29 pm
content: I don't have one to check, but a Keysight 34465A DMM can measure frequency over your specified range, claims to be able to make 1000 readings/sec with a 1ms counter gate time, and has a graphical trend display. Maybe this would solve your problem? Contact Keysight tech support for a definitive answer.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: August 01, 2019, 10:53:00 pm
content: Have you considered HP53310 modulation domain analyzer? It is an instrument designed to show frequency as a function of time on a scope-like display.