oil temp combo gauge bench testing, what am I doing wrong (question answered) next: calibrate the gauge |
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oil temp combo gauge bench testing, what am I doing wrong (question answered) next: calibrate the gauge |
malcolm2 |
Oct 14 2014, 09:00 PM
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#1
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Advanced Member Group: Members Posts: 2,745 Joined: 31-May 11 From: Nashville Member No.: 13,139 Region Association: South East States |
I have had this gauge for a while. I also found the complete taco plate, sender etc... to set it up. I decided to test it. I tested the sender a while back in hot water and remember getting various readings as the temp increased.
I pulled out my 12v powered drill battery, put 12v + on the + terminal of the gauge and the - on the - of the gauge. ( you can't see the - wire in the picture, but it is there) The gauge moved to where it is in the picture without the sender even being connected. It did not move once the sender was connected. Inside the temp gauge are the following #s. Far left 30, at the start of the red line 156.7 and the end of the red line 170 *C The top of the paper is what is stamped on each face of the hex and the gauge part # has been edited to what you see in the picture. 1. why is the gauge moving at room temp with or with out the sender? 2. do I have this thing hooked up right? any alternate testing suggestions? 3. do I have a matched sender & gauge? |
timothy_nd28 |
Oct 21 2014, 07:15 PM
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#2
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Advanced Member Group: Members Posts: 2,299 Joined: 25-September 07 From: IN Member No.: 8,154 Region Association: Upper MidWest |
what is the resistance of the sensor when at room temperature?
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stugray |
Oct 22 2014, 12:11 AM
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#3
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Advanced Member Group: Members Posts: 3,824 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
what is the resistance of the sensor when at room temperature? I believe that the sensor is a type 2252 thermistor. 2250 Ohms at 25 C (77F) 153 ohms at 100C (212F) 42 ohms at 150C (300F) So I am not quite grasping what inserting a series resistor in the circuit will do. When the oil reaches temp ~240 F = 115C = sensor is 100 ohms. If you put a 1000 ohm series resistor in line, then when the sensor is at 240F it will be 100 Ohms and the gauge will see 1100 Ohms which it will think is 42C (107F). So all the series resistor can do is decrease resolution? (IMG:style_emoticons/default/confused24.gif) I think I will break out my spare parts as well. I have to figure out how this works to tap my datalogger into the temp sensor anyway. |
malcolm2 |
Oct 22 2014, 11:54 AM
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#4
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Advanced Member Group: Members Posts: 2,745 Joined: 31-May 11 From: Nashville Member No.: 13,139 Region Association: South East States |
So I am not quite grasping what inserting a series resistor in the circuit will do. When the oil reaches temp ~240 F = 115C = sensor is 100 ohms. If you put a 1000 ohm series resistor in line, then when the sensor is at 240F it will be 100 Ohms and the gauge will see 1100 Ohms which it will think is 42C (107F). So all the series resistor can do is decrease resolution? (IMG:style_emoticons/default/confused24.gif) Tim was trying to make the gauge go to the right place at a known temperature. It seems that the sensor is doing what it is supposed to, but the gauge is off. So I assume we were faking out the gauge pumping some additional ohms into the system to move the needle to 100*C. It worked. I got the gauge to where I estimated 100*C was. It just did not completely fix my gauge. This post is on hold for a while. I am getting extra help from Tim on this. He has a theory or two he is going to try..... more to come. (IMG:style_emoticons/default/popcorn[1].gif) |
malcolm2 |
Nov 24 2014, 07:18 PM
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#5
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Advanced Member Group: Members Posts: 2,745 Joined: 31-May 11 From: Nashville Member No.: 13,139 Region Association: South East States |
This post is on hold for a while. I am getting extra help from Tim on this. He has a theory or two he is going to try..... more to come. (IMG:style_emoticons/default/popcorn[1].gif) The results are back and the old gauge guts have been replaced with the guts of a new VDO gauge. Sender is in boiling water 212*F. The left edge of the red is 314*F. For comparison the VDO face plate is in the picture, just laying on the gauge, it is not PART of the gauge. The needle seems to have moved very close to the 200 on that dial (10 mm on both) as expected. Tim is awesome |
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