[TR] Thermal Transmitter Temperature Sender help

Sat Aug 15 15:38:19 MDT 2020

 OK.  I measured late model TR6 temp gauge and it reads 61 ohms.  If you have spare parts you can connect a wire directly from the battery to one terminal on the gauge, run a wire from the other gauge terminal to the sender on the engine.  With this setup you can measure the voltage across the gauge and/or the sender.  The voltage will be constant and radiometric to the battery voltage.  The gauge reading will be irrelevant since it is calibrated to a 10 volt supply.
Attached is a spreadsheet calculating the gauge and sender voltages for all the sensor values in the table.  The battery voltage and gauge resistance are variables so you can enter the actual battery voltage into the field at the gauge and sensor voltages will be recalculated for that value of battery voltage and gauge resistance.  

Hope this helps.

Dave 

-----Original Message-----
From: Sujit Roy <triumphstag at gmail.com>
To: DAVID MASSEY <Dave1massey at cs.com>
Cc: Triumphs <triumphs at autox.team.net>
Sent: Sat, Aug 15, 2020 1:25 pm
Subject: Re: [TR] Thermal Transmitter Temperature Sender help

Thanks. I have spare parts and I plan to create a setup on a bench. I have some documents on how to check the gauge and voltage stabilizer and noe some resistance no. If my set up models that of my stag. I will have some sanity.  My stag has a 3 speed BW35. Box.  At around 70 mph the engine speed is close to 4k rpm. Did the tr7 use a bw35. If so are these numbers similar
On Sat, Aug 15, 2020, 10:35 AM DAVID MASSEY <dave1massey at cs.com> wrote:

 That could be problematic.  If the Stag gauges work like those in the TR4-6 there is a voltage stabilizer that maintains a constant average 10 volts on the gauge.  But the original stabilizer is an early form of a PWM regulator.  The contacts will alternately apply full battery volts and zero on a proportional basis such that the average is 10 volts.  And the switching frequency is about one hertz.  The gauges react slowly enough that they average it out just fine but if you put a voltmeter on it you will see the voltage switching on and off fast enough that your meter won't have time to settle out and give a meaningful reading.  

There are after-market stabilizers available that use a solid-state IC voltage regulator providing a constant 10 volts.  If you have one of those you could get a reliable reading.  But that is if you have one of those.
All that said, if I had a resistance value for the gauge I could calculate what you would get if an IC stabilizer was installed.

Dave 

-----Original Message-----
From: Sujit Roy <triumphstag at gmail.com>
To: DAVID MASSEY <Dave1massey at cs.com>
Cc: Triumphs <triumphs at autox.team.net>
Sent: Sat, Aug 15, 2020 11:30 am
Subject: Re: [TR] Thermal Transmitter Temperature Sender help

Follow up question. Does anyone have data showing what the voltage at the gauge should be  to resistance values.
On Fri, Aug 14, 2020, 12:15 PM DAVID MASSEY <dave1massey at cs.com> wrote:

 Here are some data for the TR8.  This might be close enough for the stag:
Temp C    Temp F    Orig ohms   GTR110 ohms
50        122       332         290
55        131       275         242
60        140       227         197
65        149       193         169
70        158       158         142
75        167       134         120
80        176       114         102
85        185       99          91
90        194       85          77
95        203       74          65
100       212       60          55
105       221       51          48
110       230       44          41
115       239       37          37
120       248       32          31
125       257       28          28
130       266       24          25
135       275       21          22

If you have a source of resistors in this value range you can connect them in lieu of the sensor and check the reading to see if it is close.

Dave 

-----Original Message-----
From: Sujit Roy <triumphstag at gmail.com>
To: Triumphs <triumphs at autox.team.net>
Sent: Fri, Aug 14, 2020 11:31 am
Subject: [TR] Thermal Transmitter Temperature Sender help

I'm going to try and figure out if my Stag is running hot. The gauge always reads high 
I found a note on another forum on how to test the voltage regulator, and another forum how to calibrate the gauge.
I'm trying to figure out how to test the Thermal Transmitter Temperature Sender. Does anyone have any data on how the resistance changes with temperature?
Since most Triumph around the 70's used Smith gauges, I'm assuming the data for the Thermal Transmitter Temperature Sender would be the same.
Regards, Sujit

-- 
Sujit Roy
Cupertino, California
https://triumphstagblog.wordpress.com/

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