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Thread: Adding Temp Probe to PM2

  1. #1
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    Adding Temp Probe to PM2

    Hello,

    I added a temp probe to my salinity Apex module (a second module and second probe does seem ridiculous), and nothing changed. Then I looked up in the manual that you have to tell the module that you have to add the second, superfluous probe to the system. So I did. Now my rock-solid salinity went from 34.5-35.0 to a whopping 37.7! Alarms and text messages galore. I checked the salinity with refractometer - perfect 35.0, and Milwakee at 1.024. What's up?

  2. #2
    Frequent Contributor zombie's Avatar
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    You have to recalibrate it. What I think happened is that you calibrated it with temp compensation enabled which said the temp was 20 degrees at the time since there wasn't one. When you plugged in the temp probe temp jumped and hence salinity did too.

    You might be an engineer if...You have no life and can prove it mathematically.

  3. #3
    Master Control Freak RussM's Avatar
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    Quote Originally Posted by aarfle View Post
    Then I looked up in the manual that you have to tell the module that you have to add the second, superfluous probe to the system.
    The PM2 manual does not tell you that you must add a second temperature probe; it just says that you must have a temperature probe connected to the PM2 in order to use optional temperature compensation feature. Rather than buying a second temperature probe, you could have moved the temp probe from the base unit to the PM2, which is what many people have done when adding a PM2.
    Please do not send me PMs with technical questions or requesting assistance - use the forums for Apex help. PM me ONLY if the matter is of a private or personal nature. Thanks.

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    Thank you for the quick response. I tried, but now my salinity says now 4.6 ppt, ha! Drinking water. But the animals look fine still and other testing methods are normal, so I'm going to call it a night.

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    I tried that right off the bat and it doesn't work. The manual also states that you can't use the same probe for temperature and temp/salinity.

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    Frequent Contributor zombie's Avatar
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    Quote Originally Posted by aarfle View Post
    I tried that right off the bat and it doesn't work. The manual also states that you can't use the same probe for temperature and temp/salinity.
    That is incorrect. You can use the same probe for temp control and temp compensation for the PM2. You just have to change the name in any associated heater/chiller code to the temp probe name connected to the PM2.

    What the manual does state is that temp compensation is only applied by the temp probe in the same module. So the PM2 can only be compensated by a temp probe in the PM2. Probes in the head unit can only be compensated by a probe in the head unit. So if you say want temp compensation for pH (much less sensitive to temp) AND conductivity then you need two probes. If you just want conductivity, you can have one probe plugged into the PM2 only.

    You might be an engineer if...You have no life and can prove it mathematically.

  7. #7
    Master Control Freak RussM's Avatar
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    Adding Temp Probe to PM2

    Quote Originally Posted by aarfle View Post
    I tried that right off the bat and it doesn't work. The manual also states that you can't use the same probe for temperature and temp/salinity.
    I believe you misread or misunderstood the manual. One most definitely can use the PM2 temperature probe port with a connected temp probe as the only temperature input to the Apex system. The temp probe connected to the PM2 is perfectly usable as a general temperature probe; it does not provide a temperature input solely for salinity probe temperature compensation purposes. I used the PM2 temp probe as my primary temperature probe for the tank for years. I opted to use my Apex Classic base's temp probe port for measuring ambient temperature, but that was just my choice; I could very well have used only the PM2's temperature probe.
    Please do not send me PMs with technical questions or requesting assistance - use the forums for Apex help. PM me ONLY if the matter is of a private or personal nature. Thanks.

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