Outside temperature sensor reading higher than actual

[Chimada]

This is a new sensor, jandy aqua link.

outside temp is 90degrees, but the system shows around 97.

can I just put in a resistor to offset it to read closer to actual?

i figure a 1k resistor as per resistance charts that is the difference.

 

[mas985]

How do you know the outside temperature is actually 90F? Location is everything when measuring temperature so unless it is in the same location with the same type of sensor, it is difficult to compare measurements. I have two sensors in two locations on opposite sides of the house and they are almost never the same temperature although most of the time they are close. Both sensors use Stevenson screens to help isolate the sensors from the surrounding environment so they will read the same temperature if they were in the same location (yes, I tested this). Are you using a Stevenson screen or is the sensor directly exposed to the surroundings. If exposed, a hot side of the house or concrete can dramatically affect the temperature reading. Even exposed to the night sky can have a dramatic affect. There is a good chance that the sensor is reading the correct temperature for the environment you put it in. The problem may be where the sensor is located.

But to answer your question, you can use a resistor to offset the temperatures. But again, that may lead to even more incorrect temperatures at different times of the day.

 

[JamesW]

7.8 Temp Calibration Menu This menu allows adjustment of the temperature that is displayed on the AquaLink® RS. The temperature can only be adjusted up 4 degrees Fahrenheit or down 4 degrees Fahrenheit, see note below. 7.8.1 To adjust Temperature display Highlight MENU/HELP and press SELECT, highlight SYSTEM SETUP and press SELECT, highlight TEMP CALIBRATE and press SELECT. Use the UP/DOWN arrow keys to set values and press SELECT when finished. NOTE If the temperature is off by more than four (4) degrees, contact your local service representative.

https://images.inyopools.com/cloud/documents/jandy-aqualink-rs-owners-manual.pdf

Is the sensor in direct sun?

Put a thermometer right by the sensor to compare the temperature.

 

[Chimada]

I moved the sensor out of direct sun, but is still in the open. I measured the temp with a thermometer to compare.

So I have 2 sensors, one by the equipment and one by the solar panels. I am not sure how the system takes them to determine the temperature.


I measured the resistance of the sensors directly and they measure 97 and 95 degrees per their resistance.

The temp calibration is only for the water temp, not air. The water temp is actually really close.

 

[mas985]

I moved the sensor out of direct sun, but is still in the open. I measured the temp with a thermometer to compare.

Is the sensor and thermometer in exactly the same location (and in the shade) when comparing temperatures? Note that both types of measurements can take a few minutes to equalize temperatures if they were moved to a new location. But based upon your resistive measurements, it sounds like the sensors are reading the correct temperature. Perhaps the thermometer is not? They are not perfect either.

So I have 2 sensors, one by the equipment and one by the solar panels. I am not sure how the system takes them to determine the temperature.

The solar sensor should be directly in the sun so it will read at much higher temperatures than ambient. It is only used to determine when the solar panels are turned on. It is not used at all for air temperature. The air temperature sensor should always be in the shade and if you want it to measure accurately, you need a Stevenson screen (see below). Otherwise, the temperatures can be off by quite a bit depending on then objects in the vicinity of the sensor. The primary purpose of the air sensor is to determine when there is freezing conditions so it can activate the freeze prevention system. The "display" of air temperature is secondary.


This is what PWSs and the weather services use for temperature measurements.

 

[Chimada]

thanks for the reply. I guess my main issue with the temperature is with my solar system.
Not sure if there is a way to get around this, my thought was the temp sensors.

So I want to hear my pool, to say 88. Since outside is over 88, the solar kicks on to heat, but I want to supplement with the gas heater also on the system. It won’t do both that I can tell. Since outside air is hotter than 88, the gas doesn’t kick in.

 

[mas985]

You probably have solar priority enabled. Basically, if solar is available, then it will use that first and delay the heater. If you disable solar priority, then the heater will come on with solar.

 

[Chimada]

You probably have solar priority enabled. Basically, if solar is available, then it will use that first and delay the heater. If you disable solar priority, then the heater will come on with solar.

Thanks so much, I checked and it was enabled. Disabled it. Will also move my air sensor to a more shady spot if I can find one. I went out and checked when it was early morning and it read the same. So it is working correct. The solar temp sensor I have next to the panels and it gets full sunlight, so will leave that one there.