Philips PM6654 frequency counter - Page 1
Forum section: electronics / testgear

author: davorin
author_rank: Unknown
timestamp: June 02, 2015, 09:13:21 pm
content: Looking at the Philips PM6654 datasheet it is unclear to me what resolution it has at lower frequencies....So can it actually show if a frequency is 1.0000001 or 1.0000002 Hz?

author: dom0
author_rank: Super Contributor
timestamp: June 02, 2015, 10:07:29 pm
content: (2.5 x 10^-7 s x f) / gate timeSo for 1 Hz the resolution is about 25 mHz (at 10 meas/s).Mind you, these are very good counters and where the highest-end models Philips made for quite some time - especially considering their 2 ns time base.

author: davorin
author_rank: Unknown
timestamp: June 03, 2015, 04:21:06 pm
content: So who is besides Fluke/Philips the best frequency counter nowadays?Seems counters have vanished from the market...or I didn't look at them closely lately...Hmm...25mHz.....I would rather go with 25uHz or less if that's doable... (o;

author: edpalmer42
author_rank: Super Contributor
timestamp: June 03, 2015, 05:48:16 pm
content: How about nanoHz?Here are the readings from my counters.Racal Dana 1991/1992 measures 1 Hz as1000.XXXXXXe-3 with a 1 second gate time (measurement takes 2 seconds) or1000.XXXXXXXe-3 with a 10 second gate timeAgilent 53131A measures 1 Hz as1.XXX,XXX,XXX,X with a 1 second gate time (measurement takes 5 seconds) or1.XXX,XXX,XXX,XX with a 10 second gate timeFluke/Philips PM6681 measures 1 Hz as1.XXXXXXXXX with a 1 second gate time (measurement takes 5 seconds) or1.XXXXXXXXX with a 10 second gate time (i.e. same reading)Some counters measure period faster and/or more accurately than frequency. Odd, but true.Ed

author: tautech
author_rank: Super Contributor
timestamp: June 03, 2015, 07:36:25 pm
content: Quote from: davorin on June 03, 2015, 04:21:06 pmSiglent AWG's, the SDG1000 and 5000 series are rated 100mHz~200MHz as a counter.http://www.siglentamerica.com/pdxx.aspx?id=145&T=2&tid=16In the "documents" window, you'll find the datasheet and manuals.

author: Robert763
author_rank: Super Contributor
timestamp: September 25, 2016, 02:07:07 pm
content: Hmm,The Siglent AWGs hardly qualify as counters, it's just a utility function. Only 6 digit resolution. The two big players since Fluke dropped the PM66xx range are Keysight and Stanford Research Systems (SRS). The SRS 620 costs about $5000, The Keysight 53131A costs about $3000. The PM6654 actually compares well to these current models. Modern sub 500MHz counters use reciprocal counting were they count the reference for the period of the signal. This means fo a 1Hz signal and 10MHz refernce you can only get 8 digit resolution. There are two different ways around this. One is to use a higher reference, the other is an analog interpolator the measures how far after the last reference edge the stop signal arrived. The 53131 (and famous predecessor 5370A/B considered on of the best ever) use interpolation, the PM6654 uses a 500MHz reference (multiplied from 10MHz.

author: dom0
author_rank: Super Contributor
timestamp: September 25, 2016, 03:39:52 pm
content: There's also Spectracom. They acquired Pendulum AB which was a spin-off of Fluke's frequency measurement business, which was acquired from Philips during their T&M merger. Although it would seem that the Pendulum business has little priority for Spectracom.