Zoyi ZT-225: Temperature Reading; Cap Reading - Page 1
Forum section: electronics / testgear

author: geralds
author_rank: Contributor
timestamp: May 03, 2025, 12:35:21 am
content: Hi, I received my ZT-225 today (interim solution until I become a bit more experienced to decide whether I shd get a BM2257, or BM789, or sth else more advanced...).Just some questions on the accuracy of some readings of the ZT-225 (am a complete layman...):1. Room temperature is measured as some 26/27° (w/ and w/o temperatur probe that was included). I don't have another thermometer, so I can't compare the reading. However, 26-27° "feels" too high. It shd be rather 21-23°.Zotek states the accuracy for temperature readings to be "±(3%+5)". Does the "5" digits specs mean that a reading of 26° would still be within the stated accuracy (assuming it is indeed some 21/22°)? If not, is there a simple way to "calibrate" the temp. sensor/function?I then placed the temp. probe between two frozen ice packs for coolers, and temp. dropped down to some -20°, which should be reasonably accurate. Thereafter, temp. probes still attached, ambient room temp. was shown indeed at around 21° (pretty stable reading after a few minutes). So generally (after some "burning-in" or rather "freezing-in") temp. readings with temp. probes seems accurate.2. In Capacitance mode with test leads attached (but no cap attached) there is a reading of some 0,019 - 0,024 nF. W/o test leads it reads 0. Is this behaviour correct? Understood that with "Rel" prior to measuring I can zero out the reading with test leads attached, but just wanted to check here whether this is normal.As ever, many thanks!

author: jebem
author_rank: Regular Contributor
timestamp: July 07, 2025, 01:25:34 pm
content: Quote from: geralds on May 03, 2025, 12:35:21 amI just ordered a ZT-225 as well to complement some other multimeters I already have.It is good to have more than one meter to have a second opinion, so to speak1. Generally speaking, these multimeter types have an internal temperature sensor, probably inside the MCU chip, so they show a temperature reading that is usually higher than a comfortable room temperature (around 20 degree Censius).Inserting an external temperature probe should adjust the readings to a figure closer to the reality.Anyway, I don't pay too much attention to this DMM feature, as usually the accuracy is not really high.2. This looks to be correct. The 100 to 300pF readings are caused by the test leads parasitic capacitance.Even without test leads inserted, it is common to see some parasitic reading on most of the DMMs.So when measuring a low capacitance capacitor, like 100pF, the DMM will register around 100pF + Parasitic capacitance.To reduce this effect, we can use much shorter test leads (20cm) with alligator termination, and take advantage of theRELative measurements if the DMM features it.

author: Aldo22
author_rank: Super Contributor
timestamp: July 07, 2025, 01:42:37 pm
content: The ZT-225 has two types of temperature measurement.The built-in one, which always appears when measuring VDC, for example, corresponds relatively well with the ambient temperature (photo).The temperature probe is for measurements up to 1000°C, so it is rather coarse and in my opinion not intended for room temperature details.