Frequency Response - Page 1
Forum section: electronics / testgear

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 07, 2018, 04:46:19 am
content: Are there any general-purpose meters with AC voltage frequency response across the traditional audio range (20 Hz ~ 20 KHz)? Or do we just assume that kind of performance is the purview of specialty audio test gear?Either hand-held or bench meters, and flatness within perhaps 0.2dB?The few times I have seen it mentioned, it seems like most meters barely made it up to 1KHz (if that).Perhaps this is an arcane requirement since these days, anybody can use a computer sound card and software to conduct an automated frequency response test faster than you can just do a single measurement on a meter.

author: HKJ
author_rank: Super Contributor
timestamp: July 07, 2018, 06:03:02 am
content: High-end multimeters usual goes about 50kHz.That is meters like Fluke 289, Hioki DT4282, Brymen 869s

author: BravoV
author_rank: Super Contributor
timestamp: July 07, 2018, 06:16:16 am
content: Just few examples at AC volt true RMS spec :Fluke 287/289 -> @100 KHz accuracy -> 3.5% + 40 count at (20 KHz to 100 KHz) , while lower freq has better accuracy.Keysight/Agilent U1252B or U1253B -> @100 KHz accuracy -> 3.5% + 120 count at (15 kHz~100 KHz ), same as above, lower freq has better accuracy

author: PTR_1275
author_rank: Frequent Contributor
timestamp: July 07, 2018, 06:56:47 am
content: Would some think like the Keithley 2015 do?It has the built in source and THD measurements that can be great for testing audio equipment.

author: billfernandez
author_rank: Regular Contributor
timestamp: July 07, 2018, 11:38:14 am
content: Not a multimeter, but high performance at a reasonable cost ($450), and lots of audio frequency range test and measurement capability: the QuantAsylum 401.https://quantasylum.com/products/qa401-audio-analyzer

author: 1anX
author_rank: Regular Contributor
timestamp: July 07, 2018, 12:07:28 pm
content: Quote from: billfernandez on July 07, 2018, 11:38:14 amImpressive performance!

author: bd139
author_rank: Super Contributor
timestamp: July 07, 2018, 01:22:29 pm
content: Look out for old Fluke 8050 bench meters. They are usually dirt cheap. They are flat to 100KHz easily and will give you relative readings in dB relative including reference impedance.Also GW Instek GDM-8341 does it as well.I’ve got a Heathkit IM-5238 analogue unit that’s good to 500KHz on the bench.My Keysight U1241C is also flat to 50KHz although it only quotes 2Khz in the specs.

author: Gyro
author_rank: Super Contributor
timestamp: July 07, 2018, 01:56:42 pm
content: Oldies but Goldies...Datron 1041 / 1051 bench multimeters, True RMS, Option 01:100mV - 1kV ranges:40Hz - 5kHz: +/- 0.03% Rdg +/- 0.01% FS5kHz - 20kHz: +/- 0.06% Rdg +/- 0.02% FS20kHz - 100kHz: +/- 0.1% Rdg +/- 0.05% FS10mV Range @ >300uV:40Hz - 5kHz: +/- 0.1% Rdg +/- 0.05% FS5kHz - 20kHz: +/- 0.2% Rdg +/- 0.05% FSImpressive for the day (and today?) especially on the 4 1/2 digit 1041.

author: rstofer
author_rank: Super Contributor
timestamp: July 07, 2018, 02:49:34 pm
content: Analog Discovery 2? It uses a 14 bit ADC for the scope inputs and those same inputs are used for the Voltmeter gadget. Bandwidth around 30 MHz.https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual?redirect=1I don't think I have ever seen a specification sheet like those provided for DMMs.

author: nctnico
author_rank: Super Contributor
timestamp: July 07, 2018, 03:48:11 pm
content: Quote from: Richard Crowley on July 07, 2018, 04:46:19 amThe VC8145 has decent specs for true-RMS measurements (0.8% +50 digits) but you have to adhere to some limitations where it comes to the amplitude because it uses a log-lin converter.

author: Andreas
author_rank: Super Contributor
timestamp: July 07, 2018, 05:04:43 pm
content: Hello,I would use my scope for true RMS measurement.(many digital scopes have it nowadays).AC-Linearity in 100mV range is better than a HP34401A DMM.My scope even has a frequency generator which can be used as tracking generator for frequency response analysis.with best regardsAndreas

author: nctnico
author_rank: Super Contributor
timestamp: July 07, 2018, 06:04:15 pm
content: Even at DC an oscilloscope has an accuracy in the 1.5% to 3% range which make an oscilloscope useless for accurate amplitude measurements (unless you have ways to calibrate it and control drift).

author: 2N3055
author_rank: Super Contributor
timestamp: July 07, 2018, 09:18:26 pm
content: Quote from: nctnico on July 07, 2018, 06:04:15 pmHi res Picos are 1% at DC (my ancient 212/100 is 1%) and PicoScope 4262 is 0,25% to 1% depending of range.But DC accuracy is not so important here, but linearity. Also it is a relative measurement when using Pico FRA software.But I think Andreas is referring to a fact that because of TrueRMS converter used in HP34401A, there is a dead band around +5mV/0/-5mV where measurements are not even defined and are highly non-linear. With 20mV signal you might get 10-20% error...http://www.gellerlabs.com/34401A%20AC%20zero.htmNew 34465/70 has direct sampling (TrueVolt AC) and are superior (within frequency response range of, course)But I realized that, for instance, my Pico 212/100 gives better results in true RMS than old school thermal RMS meters, and has 50MHz bandwidth...I use it for noise measurements.Regards,Sinisa