In this life-changing episode of Master Samurai Tech Radio, Samurai Appliance Repair Man and Mrs. Samurai talk about all kinds of things appliantological.
Due to the overwhelming response we've gotten the last few days, we've extended our Labor Day tuition discount on all courses and bundles at the Samurai Tech Academy thru Sunday, 9/13! Coupon code: LABORDAY2015. Enroll here!
Industry News: we talk about the international appliance brand Beko - number one in the UK - that plans to enter the American market soon. The Turks are coming!!
Appliantology News: Check out this great post on laundry detergents--HE, non-HE, and Eco. The difference is critical for a professional tech to know! Learn how when it comes to molecules, being bipolar is a good thing. Also - helpful tips for the helpful techs who answer questions over at Appliantology.org - dealing with the different types grasshoppers.
MST News: an appliance repair veteran reveals how MST training helped him earn even more money.
Tech Talk: Voltage sag - the cause of a mysterious rash of failures in a Whirlpool VM washer. What is it? Is is the same as voltage drop? (NO!)
And, a new feature--a segment on Soft Skills! Samurai and the Mrs. discuss the sensitive issue of how to handle dog problems on your service calls.
In this killa-manilla episode of the Master Samurai Tech Radio podcast, the Samurai and Mrs. Samurai reveal the answer to every burning question you’ve ever had about anything!
Okay, okay, well we at least know you’ve been losing sleep over the mysteries of centrifugal switches and what the heck is the difference between NTC and PTC. Oh, yeah, we cover that and much, much more in what can only be called an appliance repair revelation.
Here’s a list of the meaty stuff we carve up and serve in this episode:
- New credit card readers for the EMV technology; merchant (appliance service company) liability for fraud if not using the new readers.
- Square has already issued the new EMV readers.
- Electrolux buying GE Appliances - complications, lawsuit, implications for the appliance market. Samsung and LG brought into the fray!
In this scintillating episode:
- Industry news
- Passed 4 million views on our YouTube channel! You may have been one of them!
- Correction on loading meters
- Meter current draw, input impedance, and why you should care
- Ghost voltages and open neutrals
- Lord Wiggington propositions an outlet for his wiggy
- Subscribe to our podcast on iTunes
Here are your helpful links to items we talked about in this episode:
Do you know the difference between a loading meter and a non-loading digital multimeter (DMM)? Both are critical troubleshooting tools for appliance repair and both belong in your tool bag. In this post, I'll explain the difference between these two types of meters and the situations when you would want to use each type of meter. Read, watch, and be illumined!
Most digital multimeters sold today are for testing electrical and electronic systems, such as those commonly found in appliance repair, and have high impedance input circuits, typically greater than one megohm (1 million ohms). Impedance is the term used to describe total circuit resistance which includes regular resistance, as well as resistance from reactive components such as capacitors and inductors.
Fun math fact you can use to impress the ladies: The symbol used for impedance in mathematical equations is Z. Total input impedance, Z, is the sum of resistance, R, plus capacitive reactance, Xc, plus inductive reactance, Xl.
Z = R + Xc + Xl
Once you know the total impedance, Z, you can treat it just like you would total resistance, R, in any of the Ohm's law equations.
The takeaway point here is that impedance is the term for all types of resistance in electric circuits.
Mystified by all this math and electrical terminology? You don't have to be! Our Core Appliance Repair Training course gives you a solid foundation in understanding electricity and the math involved.
A DMM’s high input impedance means that when it is placed across a circuit, it will have little impact on that circuit because it will draw hardly any current, not even measurable using common equipment. You want this for most voltage measurement applications, and it is especially important for sensitive electronics or control circuits. On these types of circuits, if you draw any measurable current with your meter, you could affect the circuit by inducing a failure mode known as "loading down,” and your measurements would be meaningless.
In contrast, other troubleshooting tools such as solenoid testers generally have low impedance input circuitry of around 10 K-ohms (10,000 ohms) or less, which means that they will draw some current when placed in a circuit. These are called loading meters because in drawing significant current they are, by definition, placing a load on the circuit being tested. While these meters aren't fooled by ghost voltages, they should only be used for testing power circuits or other circuits where the low impedance will not load down the circuit voltage or alter circuit performance. Their great strength, however, lies in the very fact that they aren't fooled by ghost voltages or open neutrals.
Ghost voltages and open neutrals are two of the major landmines waiting to trip you up while you're troubleshooting a tricky circuit on a service call. For this very reason, I always keep a loading meter in my tool bag.
I’ve encountered techs who don’t see the need for loading meters, but they learn real fast after they've wasted a lot of time or gotten their asses kicked on a service call chasing ghosts or open neutrals. If it hasn't happened to you yet, then this just means you have some fun learning experiences to look forward to!
Open neutrals are pretty self-explanatory – where the neutral side of a circuit is open either due to a break in the wire or high resistance (burnt, corroded, loose, etc.) connection. But let's talk more about those scary-sounding ghost voltages.
What are Ghost Voltages and Where are they Encountered?
Ghost voltages occur from having energized circuits and non-energized wiring (such as a “dead” wire that should be energized but has an open connection to either Line or Neutral) close together, such as in those wire harness bundles commonly found in all major appliances today. This can result in a buildup of static charge that a high-impedance meter (a DMM) will read as voltage if you place its leads between the open circuit and the neutral conductor. A low-impedance loading meter, on the other hand, will not be fooled by this ghost voltage because its high current draw will immediately discharge the static buildup.
Ghost voltages can sometimes be 80% of the actual Line voltage. Spooky! So in a 120 vac power circuit, ghost voltages will often be in the 75 to 95 vac range. In some of my videos, you'll hear me refer to these as "junk voltage." Same thing. If you don't recognize ghost or junk voltage when you see it, you'll end up wasting additional time on service calls chasing your tail and going down rabbit holes. Or worse, you'll get completely faked out and confused, unable to solve the problem.
Examples of common places you'll encounter ghost voltages in appliance repair situations are a wire with an open thermal fuse that’s near a live wire or an open neutral wire in a wire harness.
But if you really want to never get fooled by ghost voltage or an open neutral, then you'll have to learn the foundational troubleshooting techniques taught only in our Core Appliance Repair Training course.
So hopefully you can see from what we’ve talked about that one of the desirable characteristics of a loading meter (also called a LoZ meter, by the way) is that it have as low an input impedance as possible or practical and, as a result, a high current draw.
With a DMM, on the other hand, you want as high an input impedance as you can afford so it draws hardly any current and thus doesn’t affect, or load down, the circuit being tested.
Now that you have a background on loading versus non-loading meters and low input versus high input impedances, let's watch a video showing a practical comparison of a couple of different types of meters. It gets really crazy as I use one meter to measure other meters. It’s Meter Mania!