Where is a cheap place to get a decent Inductance meter? How much do these things usually cost?

Mine cost 200.00 bucks ...Mouser Electronics http://www.mouser.com/ Part #615-875B

I got one on Ebay for $40.

I found this one. Maybe some of the more knowledgeable guy's can comment.

http://store.imarketcity.com/msprlcrmewit.html

Thanks guys. My next question is, does the rotor strength change the inductance reading? I would think it does. So...if I had an inductance meter, I could change the rotor and get an idea if it is stronger or weaker, correct?
Oh, what exactly is a inductance reading a measure of?

Thanks guys. My next question is, does the rotor strength change the inductance reading? I would think it does. So...if I had an inductance meter, I could change the rotor and get an idea if it is stronger or weaker, correct?
Oh, what exactly is a inductance reading a measure of?

You could build a unit that would tell you which rotor is stronger or weaker. (it's not an inductance meter, but a simple gauss meter) If you already have a digital voltmeter, you can build the unit for about $10 in parts. I've built a few of them and they work great for comparing rotors.

RC

If I remember correctly Inductance is measured in Henry's.

Is this a good one? Looks good to me and only 24 bucks???

http://cgi.ebay.com/Digital-LCR-MultiMeter-Inductance-Meter-Tester-NEW-AR_W0QQitemZ150154937908QQihZ005QQcategoryZ25421QQ ssPageNameZWDVWQQrdZ1QQcmdZViewItem

Guys -- these meters on ebay for $30 or less are worth exactly what you pay for them.

I use test equipment everyday in my line of work and I do NOT trust my life to cheap tools. I realize we are not dealing with testing for voltages and amperages that are going to cause harm to us but the principal is the same. For good/reliable/repeatable results you are going to want/need good test equipment.

Would you want to go to a Big Event to see some cheap test equipment being used? I doubt it. Stick with the good stuff, I think it will pay off in the long run. Beckman and Fluke make excellent test equipment.

Just my .02, take it with a grain of salt.

I paid around $60 for mine... no problems so far... very consistent readings. I can't see spending big $$$ on a Fluke just to check "toy"car motors ;)

You could build a unit that would tell you which rotor is stronger or weaker. (it's not an inductance meter, but a simple gauss meter) If you already have a digital voltmeter, you can build the unit for about $10 in parts. I've built a few of them and they work great for comparing rotors.

RC
could you post what parts these are and where to get them thanks

If I remember correctly Inductance is measured in Henry's.

Henry's what?? :confused:


(c'mon, man... you knew it was going to happen...) :drunk:

could you post what parts these are and where to get them thanks

For the real simple one you need a 5 volt voltage regulator, a HallEffect sensor, and a 9 volt battery.

You could get the 9volt battery connector and the regulator at Radio Shack but they do not have the HallEffect sensor. I built one that will give positive and negative readings indicating North and South Poles, but you have to use an opamp in the circuit.

I bought the stuff through Digi-Key:

Hall Effect Sensor: # 620-1022-ND

5 volt regulator: # LM7805CT-ND

Quad OpAmp: # LM324ANFS-ND

Here are instructions on how to build:

http://www.coolmagnetman.com/magmeter.htm

http://www.coolmagnetman.com/magmetr1.htm

You also need to make something to keep the rotor about an 1/8" away from the sensor, otherwise it saturates it and you won't get a good reading.

Attached is a picture of the holder I made that works well.

RC

BTW don't get that cheap one I listed.... it doesn't have the range Novak recommends for checking. Looks like about 89 and up on E-BAY.

Maybe JB from Arcor can shed some light on this.
I know she told me at the ARCOR Worlds race that she put alot of time into finding the cheapest one that would do the right job for teching the motors. I think she paid upwards of a $100+ for it if I remember right.

JB HAS THIS ONE SHE BOUGHT,I SHOWED IT TO HER LAST SPRING....THE MAIN THING IS TO BE ABLE TO MEASURE IN THE 200uH RANGE............................................. ............................ THIS IS ON EBAY---Mastech 16-Range LC Capacitance Inductance Meter DMM
9-Range/200pF-20mF 7-Range/200uH-200H 1 YEAR WARRANTY Item number: 190145583869

I am new to BL racing i found this meter http://www.partsexpress.com/images/390-570m.jpg (http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=390-570#)will this work Thanks

Ken,
I don't think that one goes low enough. You need 200 μH (microHenries). I've found these 2 on e-bay that are acceptable. We hope to be getting one for Turn 4 very soon, hopefully for Stockified.

http://cgi.ebay.com/Mastech-16-Range-LC-Capacitance-Inductance-Meter-DMM_W0QQitemZ190145583869QQihZ009QQcategoryZ25421Q QrdZ1QQssPageNameZWD1VQQcmdZViewItem

http://cgi.ebay.com/Mastech-30-Range-LCR-Capacitance-Inductance-Meter-DMM_W0QQitemZ190145585051QQihZ009QQcategoryZ25421Q QrdZ1QQssPageNameZWD1VQQcmdZViewItem

NO IT DOESN'T GO LOW ENOUGH IT MUST HAVE A RANGE OF 200uH [MICRO HENRY]

What about the two on the end?

http://www.testextra.com/protek/pages/protek_lcr_meters_selection_guide.htm

No on both, the inductance doesn't go low enough. You need 200 uH (microHenries). Look for it on the data sheets under the title "Inductance" or "Inductance Range".

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NO IT DOESN'T GO LOW ENOUGH IT MUST HAVE A RANGE OF 200uH [MICRO HENRY]




Both the Mastech 16 and 30 models DO have the 200uH range. Enlarge pic and you will see. http://www.hobbytalk.com/bbs1/images/icons/icon10.gif

I am new to BL racing i found this meter http://www.partsexpress.com/images/390-570m.jpg (http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=390-570#)will this work Thankshttp://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=390-570hear is the site that has that meter and it does 200uh

I wish I understood what these specs mean. I don't see "200uH" exactly on those meters?

Tommygun... your PM is full... cant respond :)

I am selling my meter... it has the 200uh setting.
its a "Knight K-240C LCR"
http://www.us-instrument.com/commerce/catalog/product.jsp?product_id=2081&czuid=1188975853771

I also used this meter to sort through stock (brushed) armatures to find the ones with the lowest inductance.

I will let it go for $60 shipped

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=390-570hear is the site that has that meter and it does 200uh

doesn't it say 200mh and not 200uh?

Ken,

Your pictured meter does say 200 μF (microFarads) but that is for the CAPACITANCE range. You need the 200 μH (microHenries) in the INDUCTANCE range.

Yes it is all very confusing! :confused: Took me days of research to figure it all out... :rolleyes:

I am selling my meter... it has the 200uh setting.
its a "Knight K-240C LCR"
http://www.us-instrument.com/commerce/catalog/product.jsp?product_id=2081&czuid=1188975853771
Yep, that one seems to fit the bill! :)

I have had no problems using a meter with a minimum scale of 2mH.

Hank posted an excel spreadsheet I made of brushed motor armature inductances in September 2006 that I think started a lot of discussion on inductance meters. All the readings in that spreadsheet were all done with a 2mH range on a meter I brorrowed. I had no problem identifying the winds of a bunch of unknown armatures with that meter. Here is a link to that thread:

http://www.hobbytalk.com/bbs1/showthread.php?t=155540

The relative numbers are what is important. One turn on a brushed motor armature is 3 uH. So long as the meter is accurate in the last digit you are not going to confuse a 0.053 with a 0.050. so you can usually tell winds one turn a part on a 2mH meter scale.

For brushless it is even easier since the closest ones you need to tech are at least 2 turns apart (8.5 vs 10.5 vs 13.5).

Someone asked me a question about meter accuracy. You can use a meter with a 2mH range for this testing provided the accuracy spec on that range is 2% + 1d.

That means within 2% of actual reading with a variance of no more the "1" in the last digit. The meter I was asked about was 2% +5d. 5 digits error in the last position on a 2mH range is not accurate enough.

There's an even simpler, cheaper method of checking motor windings (brushed or brushless). The attached diagram shows how to measure resistance of the windings (instead of inductance) which is not affected by rotor strength, position, etc. The only thing that changes the resistance of a motor is temperature, so as long as the motor is near room temperature, it will produce very consistant numbers.

kevinm,

Do you have known values for all of the BL motors? Right now it is a real pain to tech the motors with different rotors. The only way up to now was too take out the rotor but your way seems a lot easier.

most are listed on novaks site, and i thought its not the rotors that makes differant readings, your major readings are comming from the cans. the differance in rotors is very minimal from what i read on novaks site.

The cans have very little to do with the readings. I have tech'd the same motor with the 4 different arms and have gotten different readings. With the rotors out the reading was same each time.

It looks like this might be a better way to tech by resistance rather than indunctance.

but the rotors are the same for the 8.5, 10.5, 13.5 and im sure alot more, same part numbers. you will get differant readings, but the same general reading, like a 13.5 will be in the "25-26" zone, and a 10.5 will be in the "35-36" zone. those just being examples. thats what i gathered from novaks website.

On my unit, I get the following readings:

13.5 - 147mV
10.5 - 100mV
8.5 - 77mV
6.5 - 55mV (LRP motor)
5.5 - 42mV
(Your mileage may vary)

All the Novak motors I've checked are fairly consistant, although the more turns the motor has, the larger the variance. But the differences between winds also gets bigger. For lower turn motors, adding a 2nd 10ohm resistor in parallel with the first one would raise the current up to 1 Amp which should double the readings.

I thought I read that Charlie from Novak said that you have to remove the arm to get an accurate reading. I think if you turn the arm, the reading will change.

I have no doubt a benchmark can be used w/ the ROTOR still in the motor...for a quick tech - then if there is any doubt...and/or need the motor could be pulled apart and tested w/o the rotor for a more accurate number (If/When needed)

...anyone out there want to DONATE one of these to the 'TOUR' - that's the ONLY way I'm going to get/use one...~~~

gezer2u, you are correct the inductance will change depending on the position and condition and or type of rotor. I have had 8.5 motors ranging from low as 14 to a high of 21 on the inductance meter and if the rotor was out it would almost always read 24 to 25.

We have started a claim rule for speedo and motors to eliminate the BS. If you think someone is cheating you can buy the motor and/ or speedo. $100 for motor and $200 for speedo.