Flux core 309L that is . Well , I can run a halfway decent bead but I
don't like the way it looks ... I get good penetration if I vee the
joint , but if I wander off center I don't get good fusion on both sides
.. I think it's going to come down to coating my joints with the Solar
flux , tacking with the MIG , then finishing the weld on the bench with
the TIG . My TIG welds ain't all that pretty , but they look a lot
better than my welds with this wire . Some of the welds will need to be
made on the truck , those will probably be done with the MIG . Though I
haven't tried the OA rig for this yet ... I mean , if ya got it , try it !
--
Snag
Let's Go Brandon !

"Snag" wrote in message news:spjncp$lbh$1@dont-email.me...

Flux core 309L that is . Well , I can run a halfway decent bead but I
don't like the way it looks ... I get good penetration if I vee the
joint , but if I wander off center I don't get good fusion on both sides
.. I think it's going to come down to coating my joints with the Solar
flux , tacking with the MIG , then finishing the weld on the bench with
the TIG . My TIG welds ain't all that pretty , but they look a lot
better than my welds with this wire . Some of the welds will need to be
made on the truck , those will probably be done with the MIG . Though I
haven't tried the OA rig for this yet ... I mean , if ya got it , try it !
---------------------

https://medium.com/@3sketchjacob/types-of-mig-welding-techniques-overview-tips-39b4319afae6
I spent several class nights practicing vertical up on a non-critical
project. It was quite a bit easier with the school's Miller than with my
little 75A Century.

Either I forgot or no one ever told me there were different types of flux
core meant to use with and without shielding gas. Could you have the wrong
one?

On 12/18/2021 5:52 AM, Jim Wilkins wrote:
> "Snag"  wrote in message news:spjncp$lbh$1@dont-email.me...
>
>   Flux core 309L that is . Well , I can run a halfway decent bead but I
> don't like the way it looks ... I get good penetration if I vee the
> joint , but if I wander off center I don't get good fusion on both sides
> . I think it's going to come down to coating my joints with the Solar
> flux , tacking with the MIG , then finishing the weld on the bench with
> the TIG . My TIG welds ain't all that pretty , but they look a lot
> better than my welds with this wire . Some of the welds will need to be
> made on the truck , those will probably be done with the MIG . Though I
> haven't tried the OA rig for this yet ... I mean , if ya got it , try it !
> ---------------------
>
> https://medium.com/@3sketchjacob/types-of-mig-welding-techniques-overview-tips-39b4319afae6
>
> I spent several class nights practicing vertical up on a non-critical
> project. It was quite a bit easier with the school's Miller than with my
> little 75A Century.
>
> Either I forgot or no one ever told me there were different types of
> flux core meant to use with and without shielding gas. Could you have
> the wrong one?
>

No , this is not one of the dual-shield wires . The problem with the
bead is that it is tall and narrow . I'm at max 88 amps (Lincoln Weldpak
100) and varying the wire speed hasn't made much difference . The bead
looks nice , minimal oxidation on top , a little on the back side . I'm
actually more concerned with the lack of fusion than the bead profile .
It may be that I just don't have the amps for SS with this machine ...
--
Snag
Let's Go Brandon !

"Snag" wrote in message news:spkun1$7th$1@dont-email.me...

No , this is not one of the dual-shield wires . The problem with the
bead is that it is tall and narrow . I'm at max 88 amps (Lincoln Weldpak
100) and varying the wire speed hasn't made much difference . The bead
looks nice , minimal oxidation on top , a little on the back side . I'm
actually more concerned with the lack of fusion than the bead profile .
It may be that I just don't have the amps for SS with this machine ...
--------------------------

I get a thinner, taller bead dragging the gun and a wider, flatter one
pushing it, with the same settings.

On Sat, 18 Dec 2021 09:28:21 -0600
Snag <Snag_one@msn.com> wrote:

<snip>
>No , this is not one of the dual-shield wires . The problem with the
>bead is that it is tall and narrow . I'm at max 88 amps (Lincoln Weldpak
>100) and varying the wire speed hasn't made much difference . The bead
>looks nice , minimal oxidation on top , a little on the back side . I'm
>actually more concerned with the lack of fusion than the bead profile .
>It may be that I just don't have the amps for SS with this machine ...

Maybe try preheating the area some with a torch first?

--
Leon Fisk
Grand Rapids MI

On 12/18/2021 8:28 AM, Snag wrote:
> On 12/18/2021 5:52 AM, Jim Wilkins wrote:
>> "Snag"  wrote in message news:spjncp$lbh$1@dont-email.me...
>>
>>    Flux core 309L that is . Well , I can run a halfway decent bead but I
>> don't like the way it looks ... I get good penetration if I vee the
>> joint , but if I wander off center I don't get good fusion on both sides
>> . I think it's going to come down to coating my joints with the Solar
>> flux , tacking with the MIG , then finishing the weld on the bench with
>> the TIG . My TIG welds ain't all that pretty , but they look a lot
>> better than my welds with this wire . Some of the welds will need to be
>> made on the truck , those will probably be done with the MIG . Though I
>> haven't tried the OA rig for this yet ... I mean , if ya got it , try
>> it !
>> ---------------------
>>
>> https://medium.com/@3sketchjacob/types-of-mig-welding-techniques-overview-tips-39b4319afae6
>>
>> I spent several class nights practicing vertical up on a non-critical
>> project. It was quite a bit easier with the school's Miller than with
>> my little 75A Century.
>>
>> Either I forgot or no one ever told me there were different types of
>> flux core meant to use with and without shielding gas. Could you have
>> the wrong one?
>>
>
>   No , this is not one of the dual-shield wires . The problem with the
> bead is that it is tall and narrow . I'm at max 88 amps (Lincoln Weldpak
> 100) and varying the wire speed hasn't made much difference . The bead
> looks nice , minimal oxidation on top , a little on the back side . I'm
> actually more concerned with the lack of fusion than the bead profile .
> It may be that I just don't have the amps for SS with this machine ...

Well, just pop on over to the shop, and try it on the Miller 212. I'm
not using it today.

Is it possible your wire speed just might be a little fast.

--
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https://www.avg.com

On Sat, 18 Dec 2021 13:14:48 -0400, Leon Fisk <lfiskgr@gmail.invalid>
wrote:

>On Sat, 18 Dec 2021 09:28:21 -0600
>Snag <Snag_one@msn.com> wrote:
>
><snip>
>>No , this is not one of the dual-shield wires . The problem with the
>>bead is that it is tall and narrow . I'm at max 88 amps (Lincoln Weldpak
>>100) and varying the wire speed hasn't made much difference . The bead
>>looks nice , minimal oxidation on top , a little on the back side . I'm
>>actually more concerned with the lack of fusion than the bead profile .
>>It may be that I just don't have the amps for SS with this machine ...
>
>Maybe try preheating the area some with a torch first?
Stainless shouldn't nees that much heat as it is a TERRIBLE heat
sink / conductor - particularly with metal that thin.

On 12/18/2021 12:22 PM, Bob La Londe wrote:
> On 12/18/2021 8:28 AM, Snag wrote:
>> On 12/18/2021 5:52 AM, Jim Wilkins wrote:
>>> "Snag"  wrote in message news:spjncp$lbh$1@dont-email.me...
>>>
>>>    Flux core 309L that is . Well , I can run a halfway decent bead but I
>>> don't like the way it looks ... I get good penetration if I vee the
>>> joint , but if I wander off center I don't get good fusion on both sides
>>> . I think it's going to come down to coating my joints with the Solar
>>> flux , tacking with the MIG , then finishing the weld on the bench with
>>> the TIG . My TIG welds ain't all that pretty , but they look a lot
>>> better than my welds with this wire . Some of the welds will need to be
>>> made on the truck , those will probably be done with the MIG . Though I
>>> haven't tried the OA rig for this yet ... I mean , if ya got it , try
>>> it !
>>> ---------------------
>>>
>>> https://medium.com/@3sketchjacob/types-of-mig-welding-techniques-overview-tips-39b4319afae6
>>>
>>> I spent several class nights practicing vertical up on a non-critical
>>> project. It was quite a bit easier with the school's Miller than with
>>> my little 75A Century.
>>>
>>> Either I forgot or no one ever told me there were different types of
>>> flux core meant to use with and without shielding gas. Could you have
>>> the wrong one?
>>>
>>
>>    No , this is not one of the dual-shield wires . The problem with
>> the bead is that it is tall and narrow . I'm at max 88 amps (Lincoln
>> Weldpak 100) and varying the wire speed hasn't made much difference .
>> The bead looks nice , minimal oxidation on top , a little on the back
>> side . I'm actually more concerned with the lack of fusion than the
>> bead profile . It may be that I just don't have the amps for SS with
>> this machine ...
>
> Well, just pop on over to the shop, and try it on the Miller 212.  I'm
> not using it today.
>
> Is it possible your wire speed just might be a little fast.
>

No , if I slow it down it burns back . I think it really needs just a
few more amps , which I ain't got . Interesting though , the bead
flattens a little after the first half inch or so . It's hard for me to
run a bead much longer than about an inch and a half on this round stuff
so they all look like crap ... at least my TIG beads look uniformly
crappy !
--
Snag
Let's Go Brandon !

On 12/21/2021 5:58 AM, Snag wrote:
> On 12/18/2021 12:22 PM, Bob La Londe wrote:
>> On 12/18/2021 8:28 AM, Snag wrote:
>>> On 12/18/2021 5:52 AM, Jim Wilkins wrote:
>>>> "Snag"  wrote in message news:spjncp$lbh$1@dont-email.me...
>>>>
>>>>    Flux core 309L that is . Well , I can run a halfway decent bead
>>>> but I
>>>> don't like the way it looks ... I get good penetration if I vee the
>>>> joint , but if I wander off center I don't get good fusion on both
>>>> sides
>>>> . I think it's going to come down to coating my joints with the Solar
>>>> flux , tacking with the MIG , then finishing the weld on the bench with
>>>> the TIG . My TIG welds ain't all that pretty , but they look a lot
>>>> better than my welds with this wire . Some of the welds will need to be
>>>> made on the truck , those will probably be done with the MIG . Though I
>>>> haven't tried the OA rig for this yet ... I mean , if ya got it ,
>>>> try it !
>>>> ---------------------
>>>>
>>>> https://medium.com/@3sketchjacob/types-of-mig-welding-techniques-overview-tips-39b4319afae6
>>>>
>>>> I spent several class nights practicing vertical up on a
>>>> non-critical project. It was quite a bit easier with the school's
>>>> Miller than with my little 75A Century.
>>>>
>>>> Either I forgot or no one ever told me there were different types of
>>>> flux core meant to use with and without shielding gas. Could you
>>>> have the wrong one?
>>>>
>>>
>>>    No , this is not one of the dual-shield wires . The problem with
>>> the bead is that it is tall and narrow . I'm at max 88 amps (Lincoln
>>> Weldpak 100) and varying the wire speed hasn't made much difference .
>>> The bead looks nice , minimal oxidation on top , a little on the back
>>> side . I'm actually more concerned with the lack of fusion than the
>>> bead profile . It may be that I just don't have the amps for SS with
>>> this machine ...
>>
>> Well, just pop on over to the shop, and try it on the Miller 212.  I'm
>> not using it today.
>>
>> Is it possible your wire speed just might be a little fast.
>>
>
>   No , if I slow it down it burns back . I think it really needs just a
> few more amps , which I ain't got . Interesting though , the bead
> flattens a little after the first half inch or so . It's hard for me to
> run a bead much longer than about an inch and a half on this round stuff
> so they all look like crap ... at least my TIG beads look uniformly
> crappy !

Sounds like preheat might just do the job for you then. Yeah, welding a
round piece is a pain. Did some six inch well casing a while back.
Fortunately the duty cycle of the cheap stick welder I was using made me
stop halfway around anyway. LOL.

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"Bob La Londe" wrote in message news:sptlvi$sop$1@gioia.aioe.org...

....Fortunately the duty cycle of the cheap stick welder I was using made me
stop halfway around anyway. LOL.

-------------------

After buying a Stick/TIG Lincoln I found a better use for my 50A buzz box
arc welder as the transformer in a homebrew 12-24V 30A battery charger. It
needed a Variac to tame it. If necessary I can still reconfigure it as a
120V stick welder.

On 12/22/2021 5:34 AM, Jim Wilkins wrote:
> "Bob La Londe"  wrote in message news:sptlvi$sop$1@gioia.aioe.org...
>
> ...Fortunately the duty cycle of the cheap stick welder I was using made me
> stop halfway around anyway.  LOL.
>
> -------------------
>
> After buying a Stick/TIG Lincoln I found a better use for my 50A buzz
> box arc welder as the transformer in a homebrew 12-24V 30A battery
> charger. It needed a Variac to tame it. If necessary I can still
> reconfigure it as a 120V stick welder.
>

That is fascinating. I do have a variac on the shelf that was planned
for a sheet plastic bending tool, nut since I discovered I could bend
poly carbonate on the brake I haven't really played with the original
idea much. My buzzbox is AC only so to use it as a charger or power
supply I'd need to add a huge bridge rectifier and some serious power
caps. Not that I couldn't. That's essentially what I did for the servo
power supply on the Hurco mill. Well the transformer wasn't quite that
big, but...

--
This email has been checked for viruses by AVG.
https://www.avg.com

On Thu, 23 Dec 2021 07:44:09 -0700, Bob La Londe <none@none.com99>
wrote:

>On 12/22/2021 5:34 AM, Jim Wilkins wrote:
>> "Bob La Londe"  wrote in message news:sptlvi$sop$1@gioia.aioe.org...
>>
>> ...Fortunately the duty cycle of the cheap stick welder I was using made me
>> stop halfway around anyway.  LOL.
>>
>> -------------------
>>
>> After buying a Stick/TIG Lincoln I found a better use for my 50A buzz
>> box arc welder as the transformer in a homebrew 12-24V 30A battery
>> charger. It needed a Variac to tame it. If necessary I can still
>> reconfigure it as a 120V stick welder.
>>
>
>
>That is fascinating. I do have a variac on the shelf that was planned
>for a sheet plastic bending tool, nut since I discovered I could bend
>poly carbonate on the brake I haven't really played with the original
>idea much. My buzzbox is AC only so to use it as a charger or power
>supply I'd need to add a huge bridge rectifier and some serious power
>caps. Not that I couldn't. That's essentially what I did for the servo
>power supply on the Hurco mill. Well the transformer wasn't quite that
>big, but...
For battery charging unfiltered is every bit as good as filtered -
and many "experts" would say better as the "pilsed charge" helps break
up suphate deposits, agitates the electrolyte, and dislodges bubbles.
Using it as a charger at up to 50 amps doesn't erven take a HUGE
rectifier. A full wave bridge that handles 50 amps is only about 1 1/2
inches square and 3/8" thick. AMd only costs a few bucks.

"Bob La Londe" wrote in message news:sq21vq$1d3v$1@gioia.aioe.org...

On 12/22/2021 5:34 AM, Jim Wilkins wrote:
> "Bob La Londe" wrote in message news:sptlvi$sop$1@gioia.aioe.org...
>
> ...Fortunately the duty cycle of the cheap stick welder I was using made
> me
> stop halfway around anyway. LOL.
>
> -------------------
>
> After buying a Stick/TIG Lincoln I found a better use for my 50A buzz box
> arc welder as the transformer in a homebrew 12-24V 30A battery charger. It
> needed a Variac to tame it. If necessary I can still reconfigure it as a
> 120V stick welder.
>

That is fascinating. I do have a variac on the shelf that was planned
for a sheet plastic bending tool, nut since I discovered I could bend
poly carbonate on the brake I haven't really played with the original
idea much. My buzzbox is AC only so to use it as a charger or power
supply I'd need to add a huge bridge rectifier and some serious power
caps. Not that I couldn't. That's essentially what I did for the servo
power supply on the Hurco mill. Well the transformer wasn't quite that
big, but...

-------------------

The rectifier is an MDQ-100A, $12.99 on Amazon. I found the 78000uF cap at a
ham radio flea market. A BeesClover 100V/100A DC meter displays the output
voltage and current. I buy from Amazon to minimize exposure of my credit
card, not because they are a great parts source. Amazon is like Radio Shack,
wide variety, uncertain availability, questionable quality.

The welder transformer has substantial uncoupled self inductance that gives
it a constant-current output curve, enough that the ripple is only about 1V
p-p at 20A DC out. The down side is poor output voltage regulation, it
droops from 57V at no load to 30V at 30A, which is still enough to charge
24V batteries but makes it dangerous to leave unattended since the voltage
won't stop rising as the battery nears full charge.

If you want lab-quality voltage and current regulation from it, add a
DPS5020 digital regulator.
https://www.electronics-lab.com/ruideng-dps5020-50v-20a-power-supply-module-review/

Without the regulator the supply can deliver up to 70A long enough to test
circuit breakers etc before its 30A output breaker trips. I have a surface
mount breaker in my solar power system that's rated for 30A but actually
trips below 19. The supply's output current limitation is from overheating,
especially the Variac's brush which may be hard to replace. I had to make
one by milling and filing a motor brush. The welder transformer I used
begins to saturate at a little over 120V in. The no-load input current rose
to 5A at 138V in, so you may want to connect the Variac for 0-120V out
instead of 0-140V.
-jsw

On 12/23/2021 9:30 AM, Clare Snyder wrote:
> On Thu, 23 Dec 2021 07:44:09 -0700, Bob La Londe <none@none.com99>
> wrote:
>
>> On 12/22/2021 5:34 AM, Jim Wilkins wrote:
>>> "Bob La Londe"  wrote in message news:sptlvi$sop$1@gioia.aioe.org...
>>>
>>> ...Fortunately the duty cycle of the cheap stick welder I was using made me
>>> stop halfway around anyway.  LOL.
>>>
>>> -------------------
>>>
>>> After buying a Stick/TIG Lincoln I found a better use for my 50A buzz
>>> box arc welder as the transformer in a homebrew 12-24V 30A battery
>>> charger. It needed a Variac to tame it. If necessary I can still
>>> reconfigure it as a 120V stick welder.
>>>
>>
>>
>> That is fascinating. I do have a variac on the shelf that was planned
>> for a sheet plastic bending tool, nut since I discovered I could bend
>> poly carbonate on the brake I haven't really played with the original
>> idea much. My buzzbox is AC only so to use it as a charger or power
>> supply I'd need to add a huge bridge rectifier and some serious power
>> caps. Not that I couldn't. That's essentially what I did for the servo
>> power supply on the Hurco mill. Well the transformer wasn't quite that
>> big, but...
> For battery charging unfiltered is every bit as good as filtered -
> and many "experts" would say better as the "pilsed charge" helps break
> up suphate deposits, agitates the electrolyte, and dislodges bubbles.
> Using it as a charger at up to 50 amps doesn't erven take a HUGE
> rectifier. A full wave bridge that handles 50 amps is only about 1 1/2
> inches square and 3/8" thick. AMd only costs a few bucks.

I'm running a 100amp rectifier on the Hurco mill. With a decent size
heat sink it was around 20 dollars if I recall. It was enough I had to
count it, but not enough I worried about it. The big power caps were a
lot more.

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"Bob La Londe" wrote in message news:sq2eo9$1b0g$1@gioia.aioe.org...

I'm running a 100amp rectifier on the Hurco mill. With a decent size
heat sink it was around 20 dollars if I recall. It was enough I had to
count it, but not enough I worried about it. The big power caps were a
lot more.

----------------------

The limit I couldn't work around was heating of the primary winding.
Although it's rated for 50A at 25 arc volts the duty cycle is 20%. I found
that an output of 30A for a few minutes followed by ~22A for half an hour
would heat it to 70C at the outer windings, measured by jamming in a fine
thermocouple after finding the hottest spot with an IR thermometer. AFAICT
20-30A is the max recommended charging current for my 105Ah marine
batteries, so I stopped trying to push the output higher. There's a current
shunt and an anti-backflow diode that also warm up, plus a reverse diode to
trip the breaker instead of blowing up the cap if it's connected to a
battery backwards.

On 12/23/2021 4:36 PM, Jim Wilkins wrote:
> The limit I couldn't work around was heating of the primary winding.
> Although it's rated for 50A at 25 arc volts the duty cycle is 20%. I
> found that an output of 30A for a few minutes followed by ~22A for half
> an hour would heat it to 70C at the outer windings, measured by jamming
> in a fine thermocouple after finding the hottest spot with an IR
> thermometer.
....

A good way to measure the temperature of the coil is with the change in
resistance. Measure the resistance cold, run some low-ish current for a
while, measure the resistance again. Keep cycling with higher currents.

Copper's tempco is +0.393 percent per degree C. Which isn't very much,
especially with the heavy winding of a stick welder. You'd likely need
to use a Wheatstone bridge.

Wouldn't distinguish the hot spots, though. But the hot spots would be
internal and indistinguishable anyhow. There's probably a rule of thumb
for the temperature gradient in a transformer.

[End of meander]

"Bob Engelhardt" wrote in message news:7EjxJ.109593$SR4.54928@fx43.iad...

On 12/23/2021 4:36 PM, Jim Wilkins wrote:
> The limit I couldn't work around was heating of the primary winding.
> Although it's rated for 50A at 25 arc volts the duty cycle is 20%. I found
> that an output of 30A for a few minutes followed by ~22A for half an hour
> would heat it to 70C at the outer windings, measured by jamming in a fine
> thermocouple after finding the hottest spot with an IR thermometer.
....

A good way to measure the temperature of the coil is with the change in
resistance. Measure the resistance cold, run some low-ish current for a
while, measure the resistance again. Keep cycling with higher currents.

Copper's tempco is +0.393 percent per degree C. Which isn't very much,
especially with the heavy winding of a stick welder. You'd likely need
to use a Wheatstone bridge.

Wouldn't distinguish the hot spots, though. But the hot spots would be
internal and indistinguishable anyhow. There's probably a rule of thumb
for the temperature gradient in a transformer.

[End of meander]

-----------------

I have the instruments to measure tenths of milliOhms which would still give
me only the average temperature. The primary is 198(?) turns of 10 AWG at 1
milliOhm per foot, rated for 17A, the secondary is 6 AWG and runs cooler.
The thermocouple let me graph the temperature rise on a laptop to observe
its approach to a steady state, and check by briefly raising the current and
then seeing if the temperature peaked and decreased. The temperature rise
rating is 115C but I wanted some margin for running safely enclosed instead
of open, accessible and hazardous. The fans on my APC inverter and T60
freezer are loud enough that I can't hear whether anything else is running
or not, like a fridge or the fan in the power supply.

The datalog spreadsheet shows that at 25V, 25A out the transformer reached
73.4C at 31 minutes, rising 0.5C per minute, and cooled slightly afterwards
at 20V, 20A, open and without the fan.

It should be fine at 20A continuously, 30A for ~10 minutes, and all it can
deliver for brief experiments. The 30A output breaker will pass 70A for
about 5 seconds and the ammeter reads to 100A.

"Jim Wilkins" wrote in message news:sq4m19$isu$1@dont-email.me...

I noticed that after swapping Variacs/Powerstats and heatsinks to eliminate
lower limits, the square of the max continuous current was approximately the
duty cycle (0.2) times the square of the welding current. This makes sense
if the limit is I^2*R heating.

On 12/24/2021 9:38 AM, Jim Wilkins wrote:

> I have the instruments to measure tenths of milliOhms which would still
> give me only the average temperature. The primary is 198(?) turns of 10
> AWG at 1 milliOhm per foot, rated for 17A, the secondary is 6 AWG and
> runs cooler. The thermocouple let me graph the temperature rise on a
> laptop to observe its approach to a steady state, and check by briefly
> raising the current and then seeing if the temperature peaked and
> decreased. The temperature rise rating is 115C but I wanted some margin
> for running safely enclosed instead of open, accessible and hazardous.
> The fans on my APC inverter and T60 freezer are loud enough that I can't
> hear whether anything else is running or not, like a fridge or the fan
> in the power supply.
>
> The datalog spreadsheet shows that at 25V, 25A out the transformer
> reached 73.4C at 31 minutes, rising 0.5C per minute, and cooled slightly
> afterwards at 20V, 20A, open and without the fan.
>
> It should be fine at 20A continuously, 30A for ~10 minutes, and all it
> can deliver for brief experiments. The 30A output breaker will pass 70A
> for about 5 seconds and the ammeter reads to 100A.
>

Cool!! I can see that you're well beyond any "advice" I might have
about finding temperature with resistance. I misread your "... measured
by jamming in a fine thermocouple ...".

"Bob Engelhardt" wrote in message news:jSExJ.51318$xe2.38289@fx16.iad...

Cool!! I can see that you're well beyond any "advice" I might have
about finding temperature with resistance. I misread your "... measured
by jamming in a fine thermocouple ...".
-------------------------

For automated production testing the resistance measurement would be fine,
because it could be done in a tenth of a second or less without disturbing
the rate of rise measurement, and wouldn't require the operator to
(mis)place the thermocouple. There should be separate force and sense
connections to the winding ends to eliminate variable contact resistance.
The measurement will between the inner contacts, whether they are force or
sense. Can you guess why?

For bench testing the interruption would be long enough to disturb the rate.

The forward voltage drop of a diode, such as a transistor base-emitter
junction, is another good indicator of temperature.