ohms or capacitance reading on a water valve?

[davejohnsonnola]

In house tech at a large gaming entertainment complex.

Currently furloughed and do not have equipment in front of me, but logged onto Ignitor Labs training site and trying to keep my self COVID sane by using at least some of this time to improve.

Confused as to why Wilbur-Curtis training guide calls for using  the multi meter in diode check mode for what appears to be a standard solenoid operated water valve?

Why would it read differently with leads connected in one orientation or the other?

Why won't an ohms reading work?

See page 2 Test 3 on this site:  https://cdn.wilburcurtis.com/sites/default/files/troubleshooting-guide/Troubleshooting%20Guide%20Large%20Brewer.pdf

 

 

[ECtoFix]

WHAT are YOU doing here, Dave?

<Waving "HI!">

Never mind.  Let me catch up by looking at your problem...

[ECtoFix]

I'm still researching this, but what's confusing is what Curtis (Wilbur-Curtis) is referring to as a unit of measurement using DIODE TEST. 

The meters I use in that mode do NOT display OHMS.  They display VOLTAGE.  To clarify, the DIODE TEST mode of most meters will display VOLTAGE DROP of a diode.  Beings that diodes only allow current flow in just one direction, a digital meter would display OL when FORWARD BIASED (+ input towards the arrow symbol) and typically around 0.7vdc when reverse biased (- input towards the arrow symbol).  The latter is referred to as the "avalanche" voltage in the electronics world.

Anyway, that troubleshooting guide you linked to mentions OHMS instead of VOLTAGE DROP in the DIODE TEST mode.  That doesn't make any sense.

[ECtoFix]

8 minutes ago, ECtoFix said:

a digital meter would display OL when FORWARD BIASED (+ input towards the arrow symbol) and typically around 0.7vdc when reverse biased (- input towards the arrow symbol).

Perhaps I got that backward in my description regarding the BIAS-ing part.  While I got the polarities and readings right, forward bias is negative AGAINST the arrow:

http://fourier.eng.hmc.edu/e84/lectures/ch4/node2.html

I'm getting old and forgetting more than half the crap I used to teach to students thirty years ago.

 

 

[Vance R]

The basic is the DIODE test use higher voltage than resistance to forward bias diodes for testing. This works for all diode, except High Voltage diodes for microwaves. For HV diode you need a 9 volt battery.

[ECtoFix]

ANYWAY...

Maybe CURTIS (Wilbur-Curtis) got their terminology a bit twisted regarding a meter's settings and they meant to say the meter should be set to OHMS.

?

?

I looked at the schematic from a manual on PartsTown (PDF page 27).  The solenoids all appear to be rated for 120v (AC?).  Here's that manual:

https://static-pt.com/modelManual/WC-GEMSS10A1000_spm.pdf?v=1581571875208

I'm guessing that those valves (the inlet, brew or bypass) might INTERNALLY have what's referred to as a flyback diode (sometimes called a snubber diode, commutating diode, freewheeling diode, suppressor diode, clamp diode, or catch diode).  Those have become common nowadays to prevent transient voltages from damaging delicate control boards.  After all, EVERY coil in any relay or solenoid can BRIEFLY become a VERY short-termed power source through the "powers" of induction.

An OHMMETER (NOT in diode test) reading would be skewed by reading through BOTH, a coil AND a diode - based on the ohmmeter's polarity.  In one direction, you'd be measuring pretty much JUST the solenoid valve coil alone (with its HIGH impedance) at the rated 1300Ω or less...or the coil AND the forward-biased diode (with the diode fully conducting along with the valve's coil) to get the 5Ω or MORE.

Those are my thoughts and I'm sticking to them.

[ECtoFix]

3 minutes ago, Vance R said:

The basic is the DIODE test use higher voltage than resistance to forward bias diodes for testing. This works for all diode, except High Voltage diodes for microwaves. For HV diode you need a 9 volt battery.

Thanks, Vance. 

Yes, I use an entirely different test for HV diodes in microwaves since multi meters can't do that.  A test which requires a DC voltmeter, a 9v battery and the actual diode all connected in series. 5-7 VDC in one direction and 0-0.1VDC in the other.

[Budget Appliance Repair]

@ECtoFix I've never seen a diode on a solenoid coil to dampen flyback?/EMF? voltage when voltage is cut to a a coil - I've only seen capacitors used on the coils for this purpose.

By any chance do they maybe use diodes on coils in a DC circuit and use capacitors in AC circuits that I'm more familiar with?

Edited May 25, 2020 by Budget Appliance Repair

[davejohnsonnola]

ECto,.... you do get around!

As always, enjoy and learn from your input.

 

[ECtoFix]

@Budget Appliance Repair,

You got me there!  Yup, you're right.  Diode can't be used for that in an AC circuit.  The valves in that brewer ARE 120vac, so a R-C snubber would be needed.  I guess my theorizing on that last night got a bit off after too many adult beverages.

@davejohnsonnola,

I get AROUND?  LOL!  Yes, I'm bored too.  Been stuck at home for two months now and the resort I work at is predicting 25 June re-opening.  I'm going nuts!

FWIW:  I'd be curious to hear what Wilbur-Curtis' tech support has to say about that testing method.  Give 'em a call tomorrow, would ya?  To satisfy my curiosity, I ALSO wanna know what they say about that testing procedure.

[davejohnsonnola]

Well, the Curtis folks are very responsive to their online support!

ME:
Subject: Technical Support
Message:
Curious as to why use the diode function on a multi-meter to check the coils on brew and inlet valves on a D500GT brewer instead of using ohmmeter? I'm currently furloughed and do not have a machine in front of me, but am taking the ignitor labs training series and came across this.  From the schematic this is a 120 volt ac supply and not a polarized DC circuit so I am confused and curious.

Thank for any response.

 

 

-------- Original message --------

From: TechService <TechService@wilburcurtis.com>

Date: 5/26/20 8:42 AM (GMT-06:00)
______________________________________________________________________
Good morning David, some to our coils are rectified.  Testing with diode setting is one of two ways to test.

 

 

ME: Thanks for the response, but a diode check would read in volts, not ohms?

-------- Original message --------

From: TechService <TechService@wilburcurtis.com>

Date: 5/26/20 11:38 AM (GMT-06:00)

 

 

A diode check will read in ohms.

 

Eric Contreras

Sr. Technical Service Representative
Professional Coffee Machines - The Americas

Wilbur Curtis Co., Inc. | 6913 Acco St. | Montebello, CA 90640 | USA
phone: +1 (800) 995-0417

techservice@wilburcurtis.com | www.wmfnorthamerica.com | www.schaererusa.com | www.wilburcurtis.com

 

ME: Thanks again for rapid responses.

My only meter that has that function is locked up in furloughed facility and can't remember the last time I might have used that function!

[davejohnsonnola]

ECtofix, I'm in the same "going nuts" boat. The casinos and race tracks in the rest of Louisiana are opened in various stages and occupancy, (no fans, just horse related folks at the tracks) but in New Orleans, which had some of the worst # of cases and death rates last month the big casinos and our track are still closed. Finally got the unemployment $ going after an over two month delay but am finding out that being left entirely to my self and with no structure is not a good place for me to be. 

Strange, I have no trouble packing a tool bag and driving across town to help a friend out with something, but have no desire or drive to fix my own stuff.

[ECtoFix]

4 hours ago, davejohnsonnola said:

ME: Thanks again for rapid responses.

You sure were nice to him.  I tend to be a bit curt when tech support feeds me a "line of BS" because they don't know any better.  Especially their "Sr. Technical Service Representative" , doesn't know how DIODE TEST mode works on digital multimeters that we use every day. 

Even my two el-cheapo meters I use at home display VOLTAGE DROP in DIODE TEST mode:

 

 

Here's an article I just found on-line about testing diodes with various meters and explains why DIODE TEST displays voltage instead of ohms:

Meter Check of a Diode

 

 

4 hours ago, davejohnsonnola said:

Finally got the unemployment $ going after an over two month delay but am finding out that being left entirely to my self and with no structure is not a good place for me to be. 

After this past ten weeks on an unpaid leave of absence, I was JUST able to file for unemployment this past weekend.  I had to get my district legislature's office involved to bust through the barrier that had prevented me from doing so for so long now!  Filing for unemployment and (same as for YOU) finally getting paid is an absolute friggin' NIGHTMARE.  That's especially true here in TN.

Yes, the "lack of structure" from not working has me in a rut of sedentary habits.  Not a good thing for a man my age and my already pre-existing bad habits.

My place of work parallels yours, since it also a place where many people must gather at once.  The resort I work at gets 90% of their business from CONVENTIONS.  Although they have finally announced a 25 June re-opening date, I anticipate it will be a painfully slow ramp-up.  My OWN projection is, since I'm the junior guy ( 8 yrs) in our shop of seven...and because they're NOT going to be calling EVERYONE back in until business justifies it - I don't expect to be called back in for another month or two later (mid to late summer).  I hope I'm wrong about that.

I'd given some thoughts to getting back into a service van as a field technician again (with Hobart, Whaleys or the like), but I'm just a few years shy of retirement and have absolutely NO desire to enter into the rigors and job stresses which that entails:

• I never again want to get me & all my refrigeration tools onto anyone's roof in the blazing heat of summer or with snow greeting me for my first step off the ladder.
• I never again want to be ON-CALL for a week once a month.  I did that for fourteen years and can say that I had INDEED, at some point or another, gotten called out EVERY hour on the clock.
• I never again want to work 12-18 hours a day, which seems to have become the norm in the food equipment repair field nowadays.
• ...and numerous OTHER reasons.

[davejohnsonnola]

ECto, do you still use your comcast.net email address?