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  1. #27
    Join Date
    Jul 2005
    Posts
    5,571
    Quote Originally Posted by hvaclover View Post
    Horse Hockey Pucks.

    Test does not use insulation either.

    Seems to me that a sensor that is sensitive enough will react to temp change fast enough to to work with out insulation.
    The empirical evidence always trumps theory. I'm not speculating, just relating the facts. Take it or leave it. Techs who care about getting accurate measurements need to understand that having an accurate instrument is less important than properly using the instrument that you have.. The FP clamps are more accurate than the DC clamps in that application (I've tested this directly) despite the poorer instrument accuracy of the FP. Both will however incur an error due to air movement over the clamps. Air movement across the sensors can and will cause a false reading. The sensor should be thermally lagged to the pipe. There are entire papers written on this one subject. Try Googling something like "pipe temperature measurement". You will probably run across a couple of articles on the subject written by Adolfo Wurtz, chief design engineer for FP Instruments, amongst the many others written by engineers from much larger corporations and research groups.

  2. #28
    Join Date
    Mar 2012
    Location
    west burb IL
    Posts
    95
    Not sure if it makes a difference at all but my Ak900 sensors came hot glued to the velcro and a big portion of the sensor is buried in the glue as you can see from the pics. I'm thinking that is good enough insulation not to mention the velcros and the pvc covering them.

    Based on your statements, all digital gage temp sensor clamps available in the market will provide a false reading.

  3. #29
    Join Date
    Jul 2005
    Posts
    5,571
    Quote Originally Posted by abcando View Post
    Not sure if it makes a difference at all but my Ak900 sensors came hot glued to the velcro and a big portion of the sensor is buried in the glue as you can see from the pics. I'm thinking that is good enough insulation not to mention the velcros and the pvc covering them.

    Based on your statements, all digital gage temp sensor clamps available in the market will provide a false reading.
    That's a fact of life, not an opinion. But you're taking my statements out of context. I was referring specifically to your measurements in that packaged unit. There will be high velocity condenser air moving over your clamps in that situation, and the error, more specifically the error in your suction line temp reading, will be substantially off. It will always be off, unless the surrounding temperature is exactly equal to line temperature, but in most instances the error will be negligible providing that there is no wind and no direct sunlight on the clamps. If you thermally lag the clamp to the line then the error will be greatly reduced even if not completely eliminated. An error of 0.5° is much better than an error of 10°, which I have recorded with my DC clamps in that exact application (packaged unit).

  4. #30
    Join Date
    Mar 2012
    Location
    west burb IL
    Posts
    95
    Quote Originally Posted by hvacrmedic View Post
    That's a fact of life, not an opinion. But you're taking my statements out of context. I was referring specifically to your measurements in that packaged unit. There will be high velocity condenser air moving over your clamps in that situation, and the error, more specifically the error in your suction line temp reading, will be substantially off. It will always be off, unless the surrounding temperature is exactly equal to line temperature, but in most instances the error will be negligible providing that there is no wind and no direct sunlight on the clamps. If you thermally lag the clamp to the line then the error will be greatly reduced even if not completely eliminated. An error of 0.5° is much better than an error of 10°, which I have recorded with my DC clamps in that exact application (packaged unit).
    Got ya. It wasn't clear to me what you meant on your post. Thanks for the suggestion.

  5. #31
    Join Date
    Aug 2012
    Location
    Tennessee
    Posts
    67
    I'm still rocking the Yellow Jacket manifold and the fluke116 with the pipe clamp type k thermocouple... Old school

  6. #32
    Join Date
    Mar 2012
    Location
    west burb IL
    Posts
    95
    Hey Cmstech, whatever works good for you, that's what matters.

  7. #33
    Join Date
    Mar 2007
    Location
    wedged in freezer shelf
    Posts
    6,738
    Quote Originally Posted by hvaclover View Post
    Horse Hockey Pucks.

    Test does not use insulation either.

    Seems to me that a sensor that is sensitive enough will react to temp change fast enough to to work with out insulation.
    Clover, You are changing this with comparing different clamp designs. If all you changed with a clamp design was mass it would only just react faster to temperature change and reach the inaccurate measurement faster. An example would be your Fieldpiece clamp. If all you changed was how thin the thermocouple plate was it would react faster to temp change but would still be influenced the same from the environment around the clamp.
    “If You Can Dodge A Wrench You Can Dodge A Ball”

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