Uni-T UT20B multimeter square wave output test --  what is this ? - Page 1
Forum section: electronics / testgear

author: ez24
author_rank: Super Contributor
timestamp: October 21, 2015, 06:39:08 am
content: Uni-T UT20BFrom manual :-----------------------C. Square Wave OutputWarningTo avoid damages to the Meter, do not allow output terminals to reach higher than 10V.To measure square wave output proceed as follows:1. Set the rotary switch to (square wave symbol)2. Connect the test leads across with the object being measured.The measured value shows on the display.NoteThe frequency is approx. 50Hz.The output voltage range will be over 3Vpp when it is loaded 1M ?When square wave output testing has been completed, disconnect the connection between the testing leads and the circuit under test.--------------------------------------------------------------------------What is this for ? What object? What is measured? What units?Would the voltage (from the 10 volt warning) increase with a smaller load?FYI Manual -->http://uni-trend.com/manual2/UT20B%20Eng%20Manual.pdfthanks

author: GNU_Ninja
author_rank: Regular Contributor
timestamp: October 21, 2015, 07:34:39 am
content: It's a signal injector.http://www.electroschematics.com/9455/signal-injector-circuit/As I recall, that particular meter can output a square wave that you can use to fault find the stages of a circuit (usually audio amplifier stages). Just google 'signal injector/tracer' and you'll find lots of examples.

author: ModemHead
author_rank: Frequent Contributor
timestamp: October 21, 2015, 12:26:32 pm
content: Quote from: ez24 on October 21, 2015, 06:39:08 amThis "feature" appears on some of the cheapie 830-style models. I've never had one of these meters to confirm, but it sounds like it is just the LCD backplane signal, probably (hopefully?) buffered through a spare CMOS gate or something.

author: ez24
author_rank: Super Contributor
timestamp: October 21, 2015, 03:31:43 pm
content: Quote from: GNU_Ninja on October 21, 2015, 07:34:39 ambecause of this statementQuotethat throws me.My guess is that it is outputting a square wave and the amplitude is what shows on the display and is variable depending on the load. Seems a dangerous test since the amplitude cannot be controlled. Even the instructions say do not let it get over 10 volts with a 12 v battery?

author: GNU_Ninja
author_rank: Regular Contributor
timestamp: October 21, 2015, 03:46:02 pm
content: Try 'measuring' across some resistors with your meter set to square wave mode, see what you get. If you measure across a 1M resistor does it read 3 Vp-p?BTW the manual does give further info on the square wave source: "Output approx. at 50Hz square wave. As a simple signal source with 47k? resistance output."

author: ez24
author_rank: Super Contributor
timestamp: October 21, 2015, 04:06:31 pm
content: Quote from: GNU_Ninja on October 21, 2015, 03:46:02 pmIf I get this meter I think I would set up a pot to have a variable output square wave. I missed the addition info but that makes it more confusing.thanks

author: GNU_Ninja
author_rank: Regular Contributor
timestamp: October 22, 2015, 08:54:39 am
content: Quote from: ez24 on October 21, 2015, 04:06:31 pmSave your money and put it towards getting a better meter. The square wave output on this thing is just a gimmick. Check out some of Daves tutorials on selecting a decent budget multimeterAll I want in a basic meter is:True RMSAutorangingVoltsAmpsOhmsContinuityHold, & Min/Max functionsProperly CAT III ratedFor the record I use a Fluke 115

author: ez24
author_rank: Super Contributor
timestamp: October 22, 2015, 03:53:05 pm
content: Quote from: GNU_Ninja on October 22, 2015, 08:54:39 amI am looking for the smallest multimeter - regardless to quality or features or price.So far it looks like the Uni-T - sorry I forgot to say this - this model came from another post on the "smallest multimeter". If within a week I cannot find a smaller one, then I will order the Uni-T, I was just wondering what the square wave was for and how to use it. Being a gimmick makes the most sensethanks