Dual measurement, volt + milliamp - Page 1
Forum section: electronics / beginners

author: JanJansen
author_rank: Frequent Contributor
timestamp: April 26, 2017, 01:13:02 pm
content: Hi, i am looking to the Hameg HMC8012 multimeter.It seems they have a dual measurement function, for volt + milliamp together.I am curious : how would you connect the cables to do this measurement ?Anyone has the HMC8012 and using the dual measurement function ?thanks

author: Zero999
author_rank: Super Contributor
timestamp: April 26, 2017, 01:40:02 pm
content: Voltage is measured between the voltage input and common terminals.Current is measured between the current input and common terminals.The current shunt resistor is between the current input and common terminals.Connect the common to 0V on the power supply, the +V to the voltage input and the load between the +V and current input.

author: jeroen79
author_rank: Frequent Contributor
timestamp: April 26, 2017, 01:44:39 pm
content: My guess:

author: JanJansen
author_rank: Frequent Contributor
timestamp: April 26, 2017, 01:58:38 pm
content: So i need extra cables ?, i did not expected that, and you only get 1 set of cables with the thing i think.Maybe someone who has the HMC8012 can show me how they connected it ?If i can afford the multimeter, i cannot buy a extra cable, totally broke, maybe i have to call the shop for extra cables or discount.By the way : what would happen if you connect it wrong ?, will it break or give a negative reading or error ?

author: jeroen79
author_rank: Frequent Contributor
timestamp: April 26, 2017, 02:14:42 pm
content: What you could do wrong is:Place the voltmeter in series with the DUT --> No current will flow, as the voltmeter is high impedance.Place the ammeter parallel to the PSU --> Multimeter fuse will blow or PSU will go to CC mode, current will bypass the DUT, as the ammeter is almost a short.If you use the left wiring scheme the voltage and current will have the correct sign.The light wiring scheme will have the sign for voltage and current inverted as the Common jack is on the 'high' side.Cables aren't that expensive, less than €10 for a pair:https://www.eoo-bv.nl/484-meetsnoeren-4mm

author: Zero999
author_rank: Super Contributor
timestamp: April 26, 2017, 02:37:53 pm
content: Quote from: jeroen79 on April 26, 2017, 01:44:39 pmYes, either of those will work. At DC: the schematic on the left is what I described and would give positive readings and the one on the right hand side would give negative readings. For AC or measuring power (assuming it can do that) both configurations, would give a positive reading, since converting to RMS or multiplying negative by negative always gives a positive number.

author: rstofer
author_rank: Super Contributor
timestamp: April 26, 2017, 03:27:56 pm
content: See the diagram on Page 61 here:https://cdn.testequity.com/documents/pdf/GDM8341-GDM-8342-um.pdfNote that there are two return leads from the amps side of the meter. This doesn't apply to the Hameg, there is only one input jack. Just look at the 12A lead in the diagram and forget about the 0.5A lead.The point is to get the black input as close to ground as possible. In this case, it is one ammeter 'burden' above battery (-). Your measurements are accurate as far as the DUT is concerned.Short Answer:Voltage probe to volts input - redDevice ground to common input - blackPS ground (assume -) to current input - blueObviously, it must be possible to separate the PS ground from the DUT ground to insert the currrent leads.

author: JanJansen
author_rank: Frequent Contributor
timestamp: April 26, 2017, 03:31:03 pm
content: Hi, i,m sorry i dont know what a DUT stands for ?

author: JanJansen
author_rank: Frequent Contributor
timestamp: April 26, 2017, 03:38:30 pm
content: I am also confused with ground, i only use the - & + from my PSU, not ground.What is the difference with - and ground ?Ok you say PS ground (assume -), i always assume - if someone says ground, only it is not the same on my PSU ( sorry i,m not schooled ).It would be realy nice if someone can show in a movie who has the same thing.

author: Zero999
author_rank: Super Contributor
timestamp: April 26, 2017, 03:42:33 pm
content: Quote from: JanJansen on April 26, 2017, 03:31:03 pmDevice Under Test.Quote from: JanJansen on April 26, 2017, 03:38:30 pmIt's arbitrary.In a circuit running off +24V, the negative side of the supply (i.e. the negative terminal) would be referred to as ground or earth. All voltages relative to 0V will be positive numbers.In a circuit running off -24V, the positive side supply would be referred to as ground. All the voltages relative to 0V would then be negative numbers.

author: JanJansen
author_rank: Frequent Contributor
timestamp: April 26, 2017, 03:51:44 pm
content: Ok, my PSU only gives - 0v and + adjustable, no negative numbers to keep it simple,so what is the ground for in the PSU ?, the green one i dont use

author: w2aew
author_rank: Super Contributor
timestamp: April 26, 2017, 04:32:37 pm
content: Quote from: JanJansen on April 26, 2017, 03:51:44 pmThe output is floating. You can connect the green ground terminal to - or + if you need a positive or negative supply with respect to ground. My video explains this:

author: Zero999
author_rank: Super Contributor
timestamp: April 26, 2017, 04:38:13 pm
content: Quote from: JanJansen on April 26, 2017, 03:51:44 pmThe green terminal goes to the mains earth/ground connection.

author: rstofer
author_rank: Super Contributor
timestamp: April 26, 2017, 05:20:31 pm
content: More often than not, you will ignore the green (earth ground) terminal on the PS. If you power an Arduino from a PC USB port, one side of the power source is probably already at earth ground (if the PC is plugged in to a grounded outlet). You certainly wouldn't want to create a ground loop by introducing another path to earth ground when you use the external PS to power up some kind of peripheral to the Arduino.If you power the Arduino from a laptop running on batteries, you might actually want to provide an earth reference and the external PS for the peripheral devices could do that.One ground or none, never more.And then there is the earth ground you introduce when you use a scope (from the ground lead). Maybe it would be a good time to disconnect the PS earth ground.It gets complicated. Dave has a video on not blowing up a scope but it applies to earth grounds in general.

author: JanJansen
author_rank: Frequent Contributor
timestamp: April 28, 2017, 04:57:02 pm
content: Thanks for the video rstofer, i will also look at daves video ( if i have +- 40 minutes time enough ).Quote from: rstofer on April 26, 2017, 05:20:31 pmYes i already found that out : when connecting scope i had noise, without no noise,i had to take all the negative from 1 point close to the big condensator and the problem was solved.