Keithley DMM6500 : Dual measurement capability (demonstration)

hi everyone in one of my previous video i did a small unboxing video of the dmm 6500 multimeter from kisly and there is a feature of that multimeter which is quite unique and not very well documented and actually no one speaks about it on youtube well almost so i wanted to do a quick demonstration of that feature and that features the capability of the multimeter to do two measurements at the same time so essentially with one multimeter you can do the job of two multimeters or can you well yes but there are limitations so i'm going to explore a simple use case which is common and we'll also explore the limitations together stay with me the main measurement screen of the dmm6500 displays one measurement like any other multimeter but if you go into the menus you can have a secondary measurement so the first thing you you would be tempted to try for instance is to enable the secondary measurement as a dc current measurement so that you could measure both voltage and current which is pretty convenient but when you enable it you get this the wheels keep clicking and that's obviously very bad because you cannot necessarily replace these internal relays super easily and because relays are mechanical components they have a limited number of cycles so essentially if you keep that in the in this mode for too long you're going to reduce the lifespan of the multimeter and you don't want that so how can we do it well the reason the relays are clicking is because both measurements are in automatic range mode and the current um the i mean the the current conditions uh in which the multimeter is is that the ranges do not match so you have to force a certain range on both measurements in order for the relay not to click so let's see how we can do that um so let's go back to the settings of the current measurement the primary it's called the primary measurement in kisly language so i'm simply going to click here and i'm going to force that for instance to 10 volts and then if i enable it it keeps clicking but i can swap which means that the current measurement is now here and then in the settings i can now change the measurement range and you see if you select measurement ranges with matches with each other then you no longer get the click so that's exactly what we want so now if i go back here i can see that i have both voltage and current at the same time so that's great because it means that you have two multimeters in one package so essentially you pay for one multimeter and you get two of them or do you well yes and no you do but there are some limitations and the major limitation is that um you're going to have um a coupling between the two measurements if you have two multimeters they would be entirely floating uh if you compare their voltage reference with each other so you can collect them the way you want you can do the measurements the way you want but because there is a shared terminal between the voltage measurement and the current measurement so that's essentially the middle terminal here you're going to have to be a little creative if i could say uh to to be able to do both voltage and correct measurement at the same time and there will be situations where you will not be capable of doing the measurements simply depending on what exactly you want to measure so do not expect this instrument to replace two separate multimeters however in a pinch it's definitely going to be super helpful and it's definitely a selling point when you compare it with other multimeters which don't have that feature so i'm not saying it's a bad feature but you just have to be mindful of the limitations uh you you cannot necessarily have the range you want and also you have this shared terminal here which can be a problem in some situations so now that i've told you how to enable that feature and know that i've told you the major limitation about it what we're going to do is we're going to try it and we're going to see if it works and we're going to see how we can work around the limitation in a real life measurement so we have a 5 volt input here our 3.3 volt output from the dcc converter and our multimeter and now what we want to do remember is measure both the voltage at the output of the dc-dc converter and the current that goes from the airport to the load so let's wire the multimeter for the voltage first so what we're going to do simply is to connect the output of the converter to the road connect the positive if i can call it the positive side of the multimeter like this and the negative to ground easy enough right and now what about the current we want to measure the current what we're going to do is super simple um yes this pretty pretty easy nothing special and now we want to combine both measurements so if we look for a second at the measurement that we have on the multimeter we have a problem we have a problem because remember the terminal when you do the measurement the terminal at the center here is shared between the two measurements and in voltage measurement mode it's connected to ground but in current measurement mode well both the the the two terminals for the measurements are referenced to the frequency volt rail here so how can we make that work because it seems like we can't right well there is a solution but we have to be a bit creative let me show you so we have to do the current measurement and there are no 30 ways to do it so we're going to wire it like this but again if it's white like that um you you can't use the positive well the positive terminal of the voltage measurement so what you're going to do is something a bit contradictive you're going to connect it to ground because when you do that your current measurement is fine and it's just going to invert the reading you're going to get for the voltage right so you'll be able to do both voltage and current measurement in that situation so as you see yes you can do two measurements at the same time but you have to deal with the limitation of that terminal at the center here being shared with um the two measurement mode and there will be situations where it means that you won't be able to use the dmm6500 to do two measurements at the same time or at least not the measurements that you you want to do so just keep that in mind what we're going to do now is put that in practice and do a measurement on one liter project to see how it works uh in the real world this is a little project i'm working on it uses a five volt input 5.5 that's some proposed but let's say it's five volts it doesn't really matter and there is a small dc-dc converter right here that supplies frequent revolt to the rest of the board so what i want to do is measure the voltage of this dc-dc converter the voltage output and also how much current goes to the rest of the circuit what i'm going to do is do the wiring as per the previous diagram the first thing to do obviously is to isolate the output of the dc-dc converter from the rest of the circuit so this is the output of my dc-dc converter on this wire here [Music] and if you remember from the previous diagram the output of the dc-dc converter was going to one of the terminals of the key sleeve and specifically this one here [Music] okay that's one and now i have to connect the load and if you remember from the previous diagram the load was being connected to another output another terminal of the keystroke that's normal we want the kisly to be in series between the dcc converter and the load so we connect it like this and finally for the voltage measurement we have to connect the top terminal of the key sleeve to ground so i'm simply going to use a jumper wire between the ground of the power supply which is my system ground and the clear screen and now that everything is connected i'm just going to start power supply and we're going to see if it works seems like it does so let's see what we have the current is approximately 80 milliamps and the voltage is 3.2 volts 3.26 and notice the minus sign here but that's because as i explained before we have connected the positive side of the voltage measurement to ground due to the limitations of the the center pin of the multimeter being referenced to the frequency rail but it still gives you the voltage you want so that's it that's what i wanted to show you i would like to thank the subscriber who gave me the idea to do this short video i hope it was helpful to you it also demonstrates that the kisly is really a groundbreaking instrument in my opinion it has a lot of interesting features like this one it's not perfect but there will be situations where you you need an extra multimeter and it can uh it can help you not it won't work all the time but when it works it's pretty helpful so i hope that you enjoyed this video and uh well see you next time you

Channel: The Bootloader

Views: 2,465

Rating: 4.9452057 out of 5

Keywords:

Id: Z7sYUL85jTc

Length: 11min 22sec (682 seconds)

Published: Mon Dec 21 2020