Starting voltage for Duty cycle measurments.  - Page 1
Forum section: electronics / general

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: December 04, 2011, 03:33:02 pm
content: Well I am a bit confused about duty cycle.There is some multimeters with different minimum input level in volts Peak to Peak so to measure properly duty cycle.And I have to ask what is the minimum requirements in input voltage that some one will use in electronics.I simple words if a multimeter needs a minimum of 5 volts so to measure properly duty cycle, its useful for measuring the duty cycle in PWM fan at 5V, plus any fan with higher voltage.But is this specification good enough for a wider use ?

author: Armin_Balija
author_rank: Regular Contributor
timestamp: December 04, 2011, 06:23:27 pm
content: I would say it depends on the voltage threshold your circuit needs to see a HIGH signal in logic circuits?

author: Simon
author_rank: Unknown
timestamp: December 04, 2011, 06:29:30 pm
content: I'm assuming the voltage given is indeed the minimum required by the meter to distinguish between high and low, a bit like I/O voltages on digital chip families

author: y33t
author_rank: Contributor
timestamp: December 04, 2011, 06:49:00 pm
content: Quote from: Kiriakos-GR on December 04, 2011, 03:33:02 pmI had performed frequency counting of a PWM signal having a 120nV amplitude. It all depends on you application and purpose, AFAIK there is no standard for this.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: December 04, 2011, 07:58:18 pm
content: The point is that would any one describe this multimeter as insensitive ?%Duty Cycle 0.1% -- 99.99%Input Frequency: 5Hz -- 500 kHz,5V Logic FamilyWhat this stands for ?

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: December 04, 2011, 08:23:27 pm
content: I think that I found some theory about that.It is about signal testing on PSU, the general specification is : Logic level high = Between 2.4 V and 5 V ( square wave) output while sourcing 200uAAC / DC Universal Input Switch Mode Power SupplyThe mystery is that I have three multimeters, the one reads 51% duty cycle the second 45% and the third 37%.And I do not know what to believe, voltage input 2.4V ( square wave) 1KHz .

author: slateraptor
author_rank: Frequent Contributor
timestamp: December 04, 2011, 08:57:46 pm
content: Quote from: Kiriakos-GR on December 04, 2011, 08:23:27 pmI'd wager to say none are believable; it looks like you're attempting to measure very close to trigger threshold.If you can increase the amplitude of your square wave (and assuming your meters are reliable), I suspect your meter measurements will converge.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: December 05, 2011, 11:31:22 pm
content: I will get in few hours one professional signal generator with 0-20V PP and I will retest.

author: slateraptor
author_rank: Frequent Contributor
timestamp: December 06, 2011, 12:23:35 am
content: Quote from: Kiriakos-GR on December 05, 2011, 11:31:22 pmSweet. Let us know how it turns out.

author: Short Circuit
author_rank: Frequent Contributor
timestamp: December 06, 2011, 12:51:52 am
content: "5V Logic" means nothing, it all depends on the signalling levels. 5V TTL is very different from 5V CMOS.