Temperature error on VP2 console?

[Kurgan]

I have a new (wired) VP2, still testing it on my desk. After being on AC power (with backlight off) for a couple of days, the VP2 console that sits vertically on the table next to the ISS sensors shows 1 to 1.4 degrees (Celsius) more than the ISS. (I mean that internal temperature is higher than external) Also humidity seems to be a little lower on the console than on the ISS (46% out, 44% in, for example)

I have read that the sensors in the console could be affected by heat generated inside of the console itself.

Is this difference (1 to 1.4 degree and  2 to 3 % hum) "normal" or is it too much?

[jerryg]

I would not be concerned by those readings, keep in mind that the specs on humidity elements can cause the readings to be off from each other by that much very easily and the temp in the console is generally not going to read the same as the sensor in open air because of the air not being circulated very well around the console.

[Kurgan]

Thanks. I have just come back home to find temperature and humidity that are exactly the same. Since I will not install the ISS outside for at least five days, I will continue to monitor them anyway.

[tomcj2]

    A man with a watch knows what time it is. A man with two watches is never sure.
   
    Segal's Law

[Kurgan]

Tom, you are right.

It seems that at about 20 degrees C the two sensors agree, and when it's hotter (now 22.6 "in" and 21.0 "out") the "out" sensor measuers a lower temp. I will set up an experiment with a hotter and a colder environments later.

If I see a trend, maybe I have a defective sensor in the ISS.

[belfryboy]

I really wouldn't be that bothered about the differences between the two. There will be a lag between them purely for the fact that one is confined within a (almost) sealed box and the other is open to circulating air.

[johnd]

If I see a trend, maybe I have a defective sensor in the ISS.

As Belfryboy says, the answer is that almost certainly your sensors are perfectly good. The error on temp readings is +/-0.5degC and 3%RH. So in comparing two sensors they can be 1degC and 6% different in RH reading and still - to a first approximation (the actual statistical analysis is more complex) - be within specification.

Then to do an accurate comparison, the console and ISS need to be in a constant temperature enclosure with a fan circulating air past the units. In any ordinary room the temperature will be changing over time and there will be temperature gradients across the room, even over relatively short distances. So given the different response time constants of the ISS and console and especially in a room with no moving air you can see all sorts of variations of up to 2degC and 10% RH between the two units and not be able to interpret the differences in any consistent way.

[Kurgan]

Thanks for your answers. I will do some more tests anyway, just for fun, in a hotter and colder environment. I can also set up a fan in front of both units...

[Kurgan]

After setting up a fan on both units and waiting for about 30 minutes, I have identical readings. So, everything is fine, except for what seems to be a very long time needed to stabilize. I thought that the sensors could be more quick to stabilize.

The interesting thing is that now both sensors agree on what was the console sensor reading. Basically, it seems that the sensor that is responding very slowly to temperature variation is the one in the ISS, not in the console. I would have bet on the opposite.

[d_l]

You could glue a small muffin fan to the back of your console and power it with an auxiliary power supply to make the console more responsive to inside temperature changes.  I've done that and can provide details if you are interested.  It works well.

[Kurgan]

Dave, here the "slow" thermometer seems to be the one in the ISS, not the one in the console...