Hey there, this is the HVAC school podcast, thanks for listening to the podcast, and today we're gon na be talking about a few words that Jim Bergman has criticized me for apparently getting wrong. Sometimes I don't remember which episode it was, but sometimes I guess I confuse the terms, resolution and accuracy specifically so we're gon na talk about that. But before we do that, I want to thank our fantastic sponsors, starting with Field peace. I want to let you know that field peace has a booth at ahr.

I'm gon na give out some booth numbers here. So if you want to write them down field, peace is gon na, be at c60 359 they're gon na be demonstrating the Jobling probes. The mr 45, which is the recovery machine that I like so much the VP 85, which is their vacuum pump. You can check it all out at the HR conference or HR Expo, I should say C 63 59 or find out more by going to field peace.com.

You can also find them at true tech tools. Tr you, tech tools, com use, the offer code, get schooled for a great discount refrigeration technologies is gon na, be a B 44:17. I will be there on Monday, the 14th that's Monday. The 14th first day of the show I will be there around 3 p.m.

if you want to stop by and say, hey that would be great, very close to them, is also another sponsor nav AK @ b 43:23 and then i'm gon na be spending a lot Of time at the solder weld booth, I'm gon na be there pretty much all day Wednesday and that's be 45 79. I'm gon na take this opportunity. Just circling back to field piece to thank them for integrating their JobLink probes. Also testo has done the same recently with their smart probes, but integrating them with measure quick makes it really easy.

I was just working on it with a tech just this morning, actually connecting the probes to the measure, quick, app, it's a beautiful, beautiful connection and they really work fantastically. If you want to see those demonstrated, have any questions to ask, you can go check out field piece at C, 60. 359, all right, so we're gon na hop right into the conversation with Jim about accuracy, resolution and precision. We have a new guest somebody who I just figured I'd, give him a shot, so Jim Bergman, thanks for joining us on the podcast, hey thanks Brian gon na hear from me again all right.

So this is a short episode. This episode is about something that Jim has assistant. Li ripped me about. I've tried to get this right six or 17 times and apparently I keep getting it wrong and that is the subject of the difference, primarily between precision and accuracy, but we'll also throw a resolution in there.

So let's talk about it in the context of taking a measurement, so when I say measuring amperage, for example, what is the difference between resolution and the accuracy of an amperage measurement, whatever you're looking at a test meter? The first thing you got to say is because we talk about accuracy resolution, how accurate is your meter, meaning the best way to think of it? I think is like shooting arrows and if you were to take a target, your search, shooting arrows at the target and the bullseye. If you could hit the bullseye every single time, you would be both precise and accurate, accurate meaning that you're hitting the center of the bullseye every single time and precise, meaning that it's precisely the same spot. You're hitting and you could be. You know if we took that same bullseye and let's say we shot a really tight group to the left top center in the bullseye right.

Well, we're still very precise if a third group very tightly but we're not very accurate, because accuracy means that we're consistently hitting the bullseye precise means that we're grouping them very accurately when you're looking at those two things just the overall term. But I think just helpful to understand because, like when we're setting micron gauges side by side, this is a real common thing, because a lot of guys don't have any way of checking the accuracy of a micron gauge, so they can pair it to another micron gauge. You can take the Accu tools, move AK gauge, sets any other blue VAX and set them side-by-side, and every single one of them will read within a few microns each other at any micron level, and that shows a great level of precision. But what that doesn't show us is accuracy, because we don't know if they're, accurate or not what we do know is they're very precise now the way that we know they're accurate is we know that they were calibrated against a reference, a source, something that we know Is a standard or as a highly accurate tool and because each one of those was calibrated against a reference source and they're all reading the same now we know that they're, precise and accurate right, and that makes sense yeah.

I think so. So an example of this would be, I think, one that we run into a lot would be infrared thermometer, where we can use an infrared thermometer to measure the difference between maybe two different breaker circuit breakers, for example, and we're not so concerned whether or not we Have the exact temperature degree number correct, but we want to know that there is some precision in the differences between temperatures, and so I guess a lot of it has to do with what is the zero point? If it's not zeroed out properly, then it might read something: that's 10 degrees off, but it's still going to be precise in that it's going to still measure the same temperature at the same point over and over again. Is that a fair way of thinking about that? Or am i doing this weird? I think it's you're on the right track. There I mean it's and our industry a lot of people, don't realize that we don't need a high degree of accuracy for every single measurement that we take, but in some cases we really do before remeasuring 120 volts on a furnace coming in.

Do we really care if it's 117 volts or 125 volts or 122 volts 123 volts? Are you gon na adjust the voltage regulator on the input of the furnace to get the voltage to exactly 220? No, I mean that doesn't exist on there. So what we're really concerned with is their voltage present or not right now, that's for the most part, because then, if we want to know, do we have a correct utilization voltage? Well, then, we might need a meter with a little bit more accuracy to it, because now we're not concerned as a voltage exists, or does it not exist, we're actually concerned, as does it exist at a level, that's high enough for the equipment to operate satisfactorily. So we know that there's a percentage of the nominal voltage that we need to be within. What is that Brian? You should know it's up your head, it's within what plus or minus 5 % we have plus or minus 5 %.

So we know if our voltage dips too low, that we're gon na have issues with maybe circuit boards and not working properly or even or because we have the transformer and there we have line voltage of low voltage. Maybe that low voltage drop down low enough that we start to have problems with the circuit board. Circuitry not working right depending on what we're doing you have to have a certain level of accuracy, a certain level of precision and then what we didn't talk about yet resolution and that's the smallest amount of change that you can resolve the resolve, meaning detect. We need to be able to detect small changes.

We might do that if we're doing combustion air zone testing we're trying to see if our caz is going to negative, we have to have a resolution of about 0.1 micron. We want to see if there's small changes in the building pressure when we're turning on other appliances that are in the combustor near zone, so we're trying to see when we turn on dryer. Does the pressure go up or does the pressure go down when we turn on the hot water tank? That's a pressure. Go up or the pressure go down, we open a door, does it go up or down? So we need to be able to resolve those small changes in pressure and we need a meter.

That's got a high enough resolution like a u-tube manometer. That reagent is a water column, might have a resolution of a tenth of an inch where a test. Oh five, ten, I might have a resolution of thousandths of an inch of water column. That's again the smallest amount of change that we can detect.

That's your resolution and typically look at meter resolution. You have a certain number accounts in a meter and then a certain number of decimal places. After that, you can resolve to so you might be able to read like one point: zero zero one volts right or it might be one point: zero, volts or five. You want one volt.

Even it just depends on the accuracy and resolution and precision of your meter right and that's all those things come into play and when you're buying a tool you want to make sure that you're buying the most accurate and precise tool you have with no more resolution Than you need, because the smaller change we can detect, usually the more expensive the product becomes, and if you don't need that resolution, there's nothing to paying for it. Well, there's also a lot of instruments that have a level of resolution built into them, meaning that gives you a number of decimal places, for example, or reads a scale that actually isn't practical in conjunction with its accuracy. Right, I mean I've run into this when you start to look at certain pressure gauges that will measure into the Pascal zone, but they may measure in the one Pascal or maybe even the tenth of a pascal as far as what it shows from a resolution standpoint. But then its accuracy is plus or minus 5 Pascal's, for example, which is an example of displaying a resolution that really isn't met out by the accuracy of the instrument.

So that's a good one. I always will go back to is humidity measurements right when we're looking at changes in wet bulb. Temperature like field piece has a set of hydrometers. Tesla has a set of hydrometers and that will resolve down into the tenth of a percent of relative humidity and tenth of degree at wet bulb.

We may not know that those are accurate but they're, usually pretty precise, in other words, looking side-by-side, they'll read right down to the tenth of a degree, wet bulb the same now. Why would that be valuable if they're not act well in the air-conditioning industry, we're always concerned with the change in wet bulb so that the change across the coil like wet, bulb in versus wet, bulb out right or temperature in versus temperature out. So the fact that those may not have the highest degree of absolute accuracy isn't so important because we're looking at the change in wet ball, not the overall absolute wet, bulb what it is now, if you are charging the air conditioner and you need to know what The returner wet ball was in the outdoor air temperature as well, then you'd need something that has a little bit more accuracy than you might if it was just measuring change as long as they're precise across their entire range a lot of these tools. It's really interesting, though you're talking about I'm not seeing quite as many tools as I used to that have a higher level of resolution than they do accuracy.

I think those are sort of going by the wayside. Let's measure quick and all the work we do with metric we're testing across the board, we're seeing better, better measurements all the way across, because we do get the chance. Like a couple months ago, I went to NIST and I took a slew of different probes with me and there's actually probably $ 100,000 or the reference instruments there, and the measurement quality was so high that we couldn't tell if NIST was right or I was right. Then they had a 20,000 dollar chilled Mir hydrometer versus a $ 70.

Let's say test no probe I was using, so the tools are getting better and better. I think really we're at a point where they're, probably the best that we're gon na see because what's happening, is where the sensors were getting smaller and smaller, and it's given us just overall a faster, better reading with higher accuracy. I mean that's just we're just seeing better and better sensors out there right across the board, no matter what you pay for them, they're all pretty darn, good yeah and just back to the difference between the resolution and the accuracy, I'm thinking. Another good example of this would be Tech's have a compound gauge, or they did historically that could measure down into the negative pressure range, and so it may be very accurate in that it might show you a true measurement from a pressure standpoint, psi standpoint, but that It doesn't have the accuracy at the resolution necessary to give you any good information when it comes to a micronic vacuum, and so there would be another example of something that's accurate, but it's not precise enough.

Yeah. That's like trying to measure microns with your analog gauges is like trying to measure feet with your car odometer. It's just not gon na work. It can't resolve those measurements, are so tiny point that the analog gauge can't resolve them or you can't resolve them.

Reading the gauge you couldn't tell the difference between the 25,000 microns and 500 microns or on that gauge, let alone the difference between a thousand and five hundred. Because now we're talking to like a millimeter of mercury, which is probably the width of the needle on the gauge and then you've got parallax, which means are you looking at the gauge straight on back in the day like the old Simpson meters used to have a Needle they had a mirror behind it needle, and that was so. You can line up the needle in the reflection with the actual needle, and then you knew you're staring straight on at it. That was your parallax to make sure that everybody was looking at the meter with exactly the same angle and exactly the same way and with the old low meters and stuff that was really important because guys and electronics and you need to get a very accurate measurement.

Let's say of a resistance or something like that, but when it gets into our analog ages, well, that's the indicator of vacuum. It's definitely not a verse ice or accurate way of doing it, and it definitely doesn't have the resolution all right. There we go there's our short episode, thanks for joining us, Jim all, right Brian. It was good talk to you and hopefully you're gon na get this resolved in your mind.

So the next time could be more precise because your accuracy is just off the charts when it comes to lectures the charts, awesome, yeah yep, all right, thanks, buddy, all right, bye.