Mystery temperature sensor

A

Andre Majorel

Guest
Found in a yoghurt maker whose heating element never turns off :

http://www.teaser.fr/~amajorel/ee/f/ti3070s2.jpg

Black plastic, 23.3 x 6.7 x 3.6 mm with two wires (red and
black) coming out of one end. Marked TI-30 70 S2.

Judging by the shape, it could be a thermocouple or an RTD. Does
anyone know what it is ?

Thanks in advance !

--
André Majorel http://www.teaser.fr/~amajorel/
It is difficult to get a man to understand something, when his
salary depends upon his not understanding it. -- Upton Sinclair
 
On 03/06/2015 09:13, Andre Majorel wrote:
Found in a yoghurt maker whose heating element never turns off :

http://www.teaser.fr/~amajorel/ee/f/ti3070s2.jpg

Black plastic, 23.3 x 6.7 x 3.6 mm with two wires (red and
black) coming out of one end. Marked TI-30 70 S2.

Judging by the shape, it could be a thermocouple or an RTD. Does
anyone know what it is ?

Thanks in advance !
Click to expand...

looks like one of those compact bimetal dome switches, try heating wiht
a hot air gun connected to DVM-R
 
On Wednesday, June 3, 2015 at 1:13:26 AM UTC-7, Andre Majorel wrote:
Found in a yoghurt maker whose heating element never turns off :

http://www.teaser.fr/~amajorel/ee/f/ti3070s2.jpg
Click to expand...

Probably a thermostat, PEPI and Klixon are manufacturers of this form
of thermal switch.

If it must be replaced, you may find that 'authorized' repair of the
appliance is required. Stocking and numbering of appliance parts is
deliberately made obscure, and covered by layers of (usually
feigned) concern using words like "tamper", "unsafe", "unauthorized".
 
On 2015-06-03, whit3rd <whit3rd@gmail.com> wrote:

Probably a thermostat, PEPI and Klixon are manufacturers of this form
of thermal switch.

If it must be replaced, you may find that 'authorized' repair of the
appliance is required. Stocking and numbering of appliance parts is
deliberately made obscure, and covered by layers of (usually
feigned) concern using words like "tamper", "unsafe", "unauthorized".
Click to expand...

Curious that two of two would say it's a thermostat even though
the wires are of different colours. Reportedly, the yoghurt
maker never clicked.

DC voltage across the device is a steady 0.0 mV.

The resistance is all over the place. Constantly changing values
centred around 1.4 k one moment, then around 105 ohms the next,
then 60, then 75... Tried shining a filament lamp on the device
to heat it. Turning the light on or off sometimes causes an
instant 30% jump in the resistance. Hours of fun.

Whatever this is, it's probably defective.

Thanks.

--
André Majorel http://www.teaser.fr/~amajorel/
It is difficult to get a man to understand something, when his
salary depends upon his not understanding it. -- Upton Sinclair
 
On 04/06/2015 10:37, Andre Majorel wrote:
On 2015-06-03, whit3rd <whit3rd@gmail.com> wrote:

Probably a thermostat, PEPI and Klixon are manufacturers of this form
of thermal switch.

If it must be replaced, you may find that 'authorized' repair of the
appliance is required. Stocking and numbering of appliance parts is
deliberately made obscure, and covered by layers of (usually
feigned) concern using words like "tamper", "unsafe", "unauthorized".

Curious that two of two would say it's a thermostat even though
the wires are of different colours. Reportedly, the yoghurt
maker never clicked.

DC voltage across the device is a steady 0.0 mV.

The resistance is all over the place. Constantly changing values
centred around 1.4 k one moment, then around 105 ohms the next,
then 60, then 75... Tried shining a filament lamp on the device
to heat it. Turning the light on or off sometimes causes an
instant 30% jump in the resistance. Hours of fun.

Whatever this is, it's probably defective.

Thanks.
Click to expand...

so nothing to loose, hack into it to see what was in there, now
pitted/corroded/spark-etched contacts perhaps. Welds do fail if it is a
thermocouple. Is it connected to mains or some sort of off-line control
circuit?
 
I expect to see that VDE compliance triangle on mains rated components only
 
On Thu, 4 Jun 2015 09:37:21 +0000 (UTC), the renowned Andre Majorel
<cheney@halliburton.com> wrote:

On 2015-06-03, whit3rd <whit3rd@gmail.com> wrote:

Probably a thermostat, PEPI and Klixon are manufacturers of this form
of thermal switch.

If it must be replaced, you may find that 'authorized' repair of the
appliance is required. Stocking and numbering of appliance parts is
deliberately made obscure, and covered by layers of (usually
feigned) concern using words like "tamper", "unsafe", "unauthorized".

Curious that two of two would say it's a thermostat even though
the wires are of different colours. Reportedly, the yoghurt
maker never clicked.

DC voltage across the device is a steady 0.0 mV.

The resistance is all over the place. Constantly changing values
centred around 1.4 k one moment, then around 105 ohms the next,
then 60, then 75... Tried shining a filament lamp on the device
to heat it. Turning the light on or off sometimes causes an
instant 30% jump in the resistance. Hours of fun.

Whatever this is, it's probably defective.

Thanks.
Click to expand...

You can't expect a device that switches mains voltage to be very
consistent when measuring those eroded contacts with a multimeter. If
the element is stuck on it's possibly been busy preventing a fire.

From s.e.c.:

---

It's an entire thermostat, made by Ka Wo in Dongguan China.

Differential is quite wide (10-35°C). maybe the 70 is the set
temperature. It will switch a few amperes at mains potential directly.

This looks more like an overtemperature cutoff device than a control
device to me, but then I have no idea how a yoghurt maker works.

---

I would be looking for a different kind of temperature sensor than
this part. To determine if his is working, pass mains voltage through
it to a suitable load such as a small light bulb (or measure it
in-circuit at mains potential). Please do it safely.



--
Best regards,
Spehro Pefhany
Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8
Microchip link for 2015 Masters in Phoenix: http://tinyurl.com/l7g2k48
 
On 2015-06-07, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:
On Thu, 4 Jun 2015 09:37:21 +0000 (UTC), the renowned Andre Majorel
cheney@halliburton.com> wrote:

The resistance is all over the place. Constantly changing values
centred around 1.4 k one moment, then around 105 ohms the next,
then 60, then 75... Tried shining a filament lamp on the device
to heat it. Turning the light on or off sometimes causes an
instant 30% jump in the resistance. Hours of fun.

Whatever this is, it's probably defective.

You can't expect a device that switches mains voltage to be very
consistent when measuring those eroded contacts with a multimeter. If
the element is stuck on it's possibly been busy preventing a fire.

It's an entire thermostat, made by Ka Wo in Dongguan China.
Click to expand...

Gordon Bennett ! I'd like to have your web search skills !

Differential is quite wide (10-35°C). maybe the 70 is the set
temperature. It will switch a few amperes at mains potential directly.

This looks more like an overtemperature cutoff device than a control
device to me, but then I have no idea how a yoghurt maker works.

I would be looking for a different kind of temperature sensor than
this part. To determine if his is working, pass mains voltage through
it to a suitable load such as a small light bulb (or measure it
in-circuit at mains potential). Please do it safely.
Click to expand...

Wouldn't a thermostat have more hysteresis than is good for the
ferments ? Either they're counting on the thermal inertia of the
water in the yoghurt to smooth the temperature variations or
there is a sensor hidden somewhere in there that I can't see.

The person who's doing the repair is as puzzled as I am and has
given up on it. The cost (time, money, effort) and the fire risk
if he gets it wrong make buying a new yoghurt maker more
attractive. So that's another one for the dump. :-/

Sorry for wasting your time. At least I've learned a few things.
Thank you all.

--
André Majorel http://www.teaser.fr/~amajorel/
It is difficult to get a man to understand something, when his
salary depends upon his not understanding it. -- Upton Sinclair
 
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