looking for MASTECH MS8229 calibration procedure - Page 1
Forum section: electronics / testgear

author: cyberfuzzy
author_rank: Contributor
timestamp: August 08, 2015, 03:18:11 pm
content: Hello,I have several MASTECH MS8229 multimeters. But some of them are out of range. Unfortunately I can't find a calibration procedure for it. I asked the manufacturer for it but it seems so that they don't want to send me that information.So I opened it up and tried to turn the trim pots. But I wasn't able find out what each potentiometer is for. There are some pictures of the pots on that page:https://www.eevblog.com/forum/testgear/re-brand-of-mastech-ms2882()-from-harbor-freight-(item-98674)/Has anyone of you a calibration procedure for the MASTECH MS8229? Or did one of you find out what the individual pots are for?Thanks a lot!Cyberfuzzy

author: joeqsmith
author_rank: Super Contributor
timestamp: August 08, 2015, 03:34:35 pm
content: I posted most of them here:https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/30/

author: cyberfuzzy
author_rank: Contributor
timestamp: August 08, 2015, 03:41:38 pm
content: Thank you joeqsmith. I'm going to try to calibrate it now :-)

author: retiredcaps
author_rank: Super Contributor
timestamp: August 08, 2015, 06:09:47 pm
content: Quote from: cyberfuzzy on August 08, 2015, 03:18:11 pmI'm curious about what is actually out range. Is it DCV or resistance? How much is it out of range by?

author: cyberfuzzy
author_rank: Contributor
timestamp: August 09, 2015, 12:40:33 am
content: @retiredcaps: I don't really know how much it is out of range because I do not have high end multimeters, voltage standards and so on. But to get an idea of it I did some measurements with four multimeters.The number in front of the following results is the number of the multimeter as you can see here:Multimeter 1: MASTECH MS8229 (original condition)Multimeter 2: MASTECH MS8229 (original condition)Multimeter 3: UNI-T UT58C (original condition)Multimeter 4: MASTECH MS8229 (opened, trim pots turned)Here are the results of some measurements:DC Voltage:(All multimeters connected to the same potential.)1. 190.5 mV2. 190.7 mV3. 189.9 mV4. 190.7 mV1. 1.884 V2. 1.889 V3. 1.883 V4. 1.894 V1. 19.52 V2. 19.61 V3. 19.51 V4. 19.70 V1. 60.0 V2. 60.3 V3. 60.0 V4. 60.4 VAC Voltage:(All multimeters connected to the same potential.)1. 1.043 V2. 1.043 V3. 1.044 V4. 1.037 V1. 18.87 V2. 18.90 V3. 18.90 V4. 18.87 V1. 194.5 V2. 195.1 V3. 199.8 V4. 194.0 V1. 277.2 V2. 278.1 V3. 278 V4. 276.6 VFrequency:(All multimeters connected to the same potential.)1. 49.99 Hz2. 49.99 Hz3. 0.047 kHz4. 49.99 Hz1. 0.999 kHz2. 0.999 kHz3. 1.000 kHz4. 0.999 kHz1. 18.99 kHz2. 18.99 kHz3. 19.06 kHz4. 18.99 kHzDC Current:(All multimeters connected in series.)1. 35.91 mA2. 36.20 mA3. 36.0 mA4. 36.37 mA1. 188.2 mA2. 189.3 mA3. 188.6 mA4. 190.1 mA1. 2.912 A2. 2.933 A3. 2.94 A4. 2.931 AAC Current:(All multimeters connected in series.)1. 0.402 A2. 0.404 A3. 0.41 A4. 0.400 A1. 3.024 A2. 3.034 A3. 3.06 A4. 3.015 AResistance:(I used a 1.82 kOhm, 1% resistor. LCR/ESR-Meter measured 1.8187 kOhm.)1. 1.818 kOhm2. 1.816 kOhm3. 1.817 kOhm4. 1.820 kOhm

author: retiredcaps
author_rank: Super Contributor
timestamp: August 09, 2015, 12:53:36 am
content: Quote from: cyberfuzzy on August 09, 2015, 12:40:33 amYou don't necessarily need a voltage standard, but a quick look through your readings, I would say all 4 meters are within their specifications. For the above measurements in your picture, the spec for ACV is 0.8% + 3 counts. Assuming 1.043 is the "correct" measurement, all the meters are easily within the 0.8% +3 counts.Even the best meters will differ 1mV or 2mV, but be within their respective specifications.In your original post, I thought you were getting readings like 1.043 on one meter and 1.542 on another meter.

author: retiredcaps
author_rank: Super Contributor
timestamp: August 09, 2015, 03:16:09 am
content: Quote from: cyberfuzzy on August 09, 2015, 12:40:33 amThe DCV for the Mastech is 0.7% + 2 counts. The UT58C is 0.5% + 1 count.Ifthe 19.52V is the correct reading, then #4 is slightly out of spec.19.52 x 0.7% = 0.13664 = 0.14 => 0.14 + 2 counts = 16 counts.So 19.52 + 0.16 = 19.68 (upper bound).PS. I haven't done the calculations for your other ranges, but given the internal build quality and components of your meters, for most purposes, it should be good enough. To get something more accurate, the meter has to have some high quality precision hybrid resistor network and/or software stored calibration offsets for each range.

author: Lightages
author_rank: Unknown
timestamp: August 09, 2015, 03:23:53 am
content: Really, for the price of cheap voltage references right now, there is no reason to not have one to check your meters:http://www.ebay.com/itm/AD584KH-4-Channel-2-5v-7-5v-5v-10v-High-Precision-Voltage-Reference-Module-Simpl-/181219600361?hash=item2a3187a7e9http://www.ebay.com/itm/KKMOON-Accuracy-Voltage-Reference-Module-AD584kH-4-Channel-2-5V-7-5V-5V-10-NEW-/131566638421?hash=item1ea1fb9555and there are more useful ones for multimeters at:www.voltagestandard.com

author: retiredcaps
author_rank: Super Contributor
timestamp: August 09, 2015, 03:28:55 am
content: Quote from: cyberfuzzy on August 09, 2015, 12:40:33 amWow, the UT58C reading is way off compared to the other 3. Since the UT58C is a 2,000 count meter, this reading is close to full scale.

author: cyberfuzzy
author_rank: Contributor
timestamp: August 09, 2015, 12:06:12 pm
content: Quote from: retiredcaps on August 09, 2015, 03:28:55 amMaybe that is because it was not a perfect sine wave? I used a transformer on mains voltage for that measurement.

author: cyberfuzzy
author_rank: Contributor
timestamp: August 09, 2015, 12:59:44 pm
content: I repeated the measurement with 198 V and 130 V. All multimeters were connected the same way as yesterday. It looks much better now.I think the deviation yesterday could be of a bad sine wave or maybe the voltage changed and the update rate of the UT58C is to slow?Today's results:AC Voltage:1. 198.2 V2. 198.8 V3. 198.7 V4. 197.7 V1. 130.4 V2. 130.9 V3. 130.9 V4. 130.0 VThe scope measures 131 V. But it is definitely not a perfect sine wave as you can see here:

author: joeqsmith
author_rank: Super Contributor
timestamp: August 10, 2015, 03:28:41 am
content: Quote from: cyberfuzzy on August 08, 2015, 03:41:38 pmNo problem. Glad to help. Let me know if you figure out what the other pots are for.

author: giorgiovi
author_rank: Newbie
timestamp: July 12, 2018, 02:28:31 pm
content: Hi,do you have procedure calibration for MS8229?Thanks

author: giorgiovi
author_rank: Newbie
timestamp: July 12, 2018, 02:42:22 pm
content: Has anyone of you a calibration procedure for the MASTECH MS8229?