Audio frequency, frequency standards? - Page 1
Forum section: electronics / general

author: Svgeesus
author_rank: Regular Contributor
timestamp: November 20, 2022, 09:50:45 pm
content: I was wondering what people use as an audio frequency standard to check their DMM against. I currently have a DMMCheckPlushttps://dmmcheckplus.com/which in addition to the voltage and current outputs also produces a 440Hz output (this was a custom configuration which they did for me). I have their Agilent 53131A Universal Frequency Counter measured result, which was fine for comparing against my 6.5 digit meter (Keysight 34465A). But now, my meter is 3 years out of cal and the standard itself is 2 years out of cal and also the crystal is a basic one, not OCXO or anything like that.I see units on ebayhttps://www.ebay.com/itm/233512235034?hash=item365e69f01a:g:iWcAAOSwOQJeXgQC&amdata=enc%3AAQAHAAAA4HuUMVxYfwNCrAoivINsYJyyzBoVBmXr%2F4oe50r1luEOyC7b%2BosnbuxYk%2FNjAIh9NZp2BwmF0aupLu8WVVZkkkpj818EDRFot16wXTKRSfHPubwMCEkmziekvFO7VUd4bFHO62bFcszs4ZWGIWMM2phdzYbxlmw7ZpR0g4G0eNfj38oRf1MNofqBbiNxoTmxaiFE5txnMqEn74gvXgO%2ByLA26a6%2FDVyExGz7KokwnyxPdLQVOnPYb%2Faiq4LdvrIg%2FdxKVseplI4yJ%2FO%2BESAkX%2B1iMXofwpGTbeGiHDBSx8gW%7Ctkp%3ABFBMtvnR7pJhthat generate word clock (44.1kHz, 48kHz, etc) from a 10 MHz OCXO but have no idea if they would be an improvement and the lowest frequency is higher than I would like.Unlike GPS-disciplined units which seem optimized to correct long-term drift, I'm looking at only short-term absolute stability and (idealy) reasonable temperature invariance over a 20C range.I considered making something from a Teensy which has a fairly good (15ppm) crystal, but it is not ovened.Other people must have faced this problem, what do you use?

author: ap
author_rank: Frequent Contributor
timestamp: November 20, 2022, 10:02:17 pm
content: You better buy a synthesizer, gives you all you need at any frequency and amplitude.

author: Svgeesus
author_rank: Regular Contributor
timestamp: November 21, 2022, 04:36:53 pm
content: > You better buy a synthesizer, gives you all you need at any frequency and amplitude.They don't come with a calibration certificate, nor any claims on accuracy and stability.

author: bdunham7
author_rank: Super Contributor
timestamp: November 21, 2022, 05:55:57 pm
content: Quote from: Svgeesus on November 21, 2022, 04:36:53 pmDo you need the certificate? I'm guessing not if your meter is 3 years out of cal. The specs for your DMM are so wide that even an ultra-budget AWG like the Feeltech FY6900 should be more than good enough, as would any reasonable frequency counter or even a DSO.

author: jonpaul
author_rank: Super Contributor
timestamp: November 21, 2022, 06:03:44 pm
content: I have same 6.6 d Keysight 34465aeither assume cal is OK or send to keysight for CAL if you need NBS traceabilityWe useleo Bodnar GPS DSO450 Hz..800 MHz$120http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=301Jon

author: MegaVolt
author_rank: Frequent Contributor
timestamp: November 22, 2022, 12:24:22 pm
content: Fluke 510A

author: alm
author_rank: Super Contributor
timestamp: November 22, 2022, 12:35:25 pm
content: The Fluke 510A is an AC amplitude standard with okay frequency stability. As frequency standard for a relatively low accuracy device like a DMM would generally be a function generator, optionally locked to an external frequency standard, or a frequency counter with either a decent (TCXO or better) time base or an external frequency reference.

author: themadhippy
author_rank: Super Contributor
timestamp: November 22, 2022, 12:44:52 pm
content: Quoteeasily cured

author: N2IXK
author_rank: Frequent Contributor
timestamp: November 22, 2022, 04:02:53 pm
content: HP 3325A, locked to an external Rb reference...

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 22, 2022, 06:27:46 pm
content: Buy a Bodnar and be done with it.

author: mendip_discovery
author_rank: Super Contributor
timestamp: November 22, 2022, 07:05:44 pm
content: A GPS reference should be enough to get you traceability.Leo unit would be great for you.My 34401A is rather stable on freq and has been within a digit for the past 6 years of calibration.