Flowki
Well-Known Member
I'm revisiting the basics of air circulation, I strangely couldn't find any specific thread on probe placements, perhaps I made the wrong searches. Anyway, hopefully some of this is useful to others, however I do have some questions myself.
I figured what is the point in trying to learn better placements if the calibration of the units are inaccurate?. To test this I purchased a laboratory grade mercury thermometer (they sound flashy but are surprisingly cheap). I also purchased some 65% humidity bovida packs.
Only one of the digital read outs was accurate according to the laboratory thermometer. Weather or not the lab mercury thermometer is 100% accurate I do not know.. but it should be far more consistent over time as a steady bench mark to check the digital therm read outs are accurate within 2%. To test this was easy, place all units close together in a room/box with a steady temperature and wait 5-10 min. However, you should suspend the lab therm in the air so it doesn't give a false reading from surface contact. It is much easier if you have hygrometers or probes that have a calibration function, just calibrate them to the lab thermometer. If they do not have this function you can write a note on the units and add/take away the difference mentally for actual rad outs. My thermometers didn't drift that far, however one was 3F out. That may not be the case with everyone, it's worth checking as it could be worse for you. The quality of goods on amazon and ebay really seems to be dropping sharply, don't trust anything to be high quality and accurate out of the box, spending more doesn't mean quality these days. Ignore 5 star reviews, read the 3 star reviews for a more realistic idea of product quality (general tip).
For the humidity read out calibration place a bovida pack in a small air tight tub. A zip bag could be used but I found that they don't hold shape well enough to allow the humidity to properly stabilise, or they just aren't that air tight?. A small see through tub was much better, especailly if you are using a probe-less hygrometer so that you can see the read out inside the tub. If you have a wired probe I do recommend you take the effort to cut a small access hole on the top of the tub to allow the wire to sit just under the lid seal. You will have to seal this with tape or bluetac. It would be tempting to just put a normal hygrometer in the tub and use that to calibrate the probed hygrometer. This isn't a good idea though, the probe-less hygrometers tend to be of cheaper quality and seem to have a much wider ''inherent'' inaccuracy range. In other words the more expensive wire probe units seem to have less natural error range so calibrating it personally will be more accurate by a few%. In the end, two of the units needed calibrating by 3>8%. Surprisingly, one of the oldest ones I had was accurate, while one of the newest ones was not. Most certainly worth testing since I've seen people complain they were out as much as 15%.
So that's the end of the part where it looks like I know my shit.
For the most part I followed basic advice on RIU in terms of placements and then just forgot about them. The temp probe is center space just below top leaves to block any radiant heat. This was older advice for HPS however I now use cobs. I'm not sure if it is still required to do that with cobs/led?. I also remove a few leaves around the probe so that it is in shade from above but not in contact with anything around or below. Again it might just be ocd but I figured surfaces of any kind could increase/reduce read outs. On the left side of the space, just under canopy level I have a suspended hygrometer. On the right side also is the same. All tend to give similar temp read outs so I feel happy with that.. although I don't know if the placements themselves are still ''ok'' for cob/led, or if I am just following old hps philosophy. I also have the laboritory thermometer suspended in the room, it is above canopy hight but not in light range or direct air circulation. It reads about 4-5f higher than the other read outs but that seems about right given it's location, do suggest otherwise if not.
The humidity probe is placed next to the temp probe, centre canopy, but I have it just peaking above canopy. I have an under canopy extraction setup that sends lower humid air into the direction of the De-huey. The de-huey is sitting under a tower fan. The under canopy humid air and dry de-huey air basically gets mixed and pulled through the tower fan, then pushed over the canopy. The humidity probe then receives some of that mixed air to check if it's in range. The far left and far right hygrometers that are just under canopy tend to read up to 5% lower humidity than the center canopy rh probe. That makes sense given the locations/under canopy airflow but again, doesn't mean it's over all a good placement. I do wonder if it creates a kinda closed loop of the de-huey fighting respiration rates? or something like that.
I figured what is the point in trying to learn better placements if the calibration of the units are inaccurate?. To test this I purchased a laboratory grade mercury thermometer (they sound flashy but are surprisingly cheap). I also purchased some 65% humidity bovida packs.
Only one of the digital read outs was accurate according to the laboratory thermometer. Weather or not the lab mercury thermometer is 100% accurate I do not know.. but it should be far more consistent over time as a steady bench mark to check the digital therm read outs are accurate within 2%. To test this was easy, place all units close together in a room/box with a steady temperature and wait 5-10 min. However, you should suspend the lab therm in the air so it doesn't give a false reading from surface contact. It is much easier if you have hygrometers or probes that have a calibration function, just calibrate them to the lab thermometer. If they do not have this function you can write a note on the units and add/take away the difference mentally for actual rad outs. My thermometers didn't drift that far, however one was 3F out. That may not be the case with everyone, it's worth checking as it could be worse for you. The quality of goods on amazon and ebay really seems to be dropping sharply, don't trust anything to be high quality and accurate out of the box, spending more doesn't mean quality these days. Ignore 5 star reviews, read the 3 star reviews for a more realistic idea of product quality (general tip).
For the humidity read out calibration place a bovida pack in a small air tight tub. A zip bag could be used but I found that they don't hold shape well enough to allow the humidity to properly stabilise, or they just aren't that air tight?. A small see through tub was much better, especailly if you are using a probe-less hygrometer so that you can see the read out inside the tub. If you have a wired probe I do recommend you take the effort to cut a small access hole on the top of the tub to allow the wire to sit just under the lid seal. You will have to seal this with tape or bluetac. It would be tempting to just put a normal hygrometer in the tub and use that to calibrate the probed hygrometer. This isn't a good idea though, the probe-less hygrometers tend to be of cheaper quality and seem to have a much wider ''inherent'' inaccuracy range. In other words the more expensive wire probe units seem to have less natural error range so calibrating it personally will be more accurate by a few%. In the end, two of the units needed calibrating by 3>8%. Surprisingly, one of the oldest ones I had was accurate, while one of the newest ones was not. Most certainly worth testing since I've seen people complain they were out as much as 15%.
So that's the end of the part where it looks like I know my shit.
For the most part I followed basic advice on RIU in terms of placements and then just forgot about them. The temp probe is center space just below top leaves to block any radiant heat. This was older advice for HPS however I now use cobs. I'm not sure if it is still required to do that with cobs/led?. I also remove a few leaves around the probe so that it is in shade from above but not in contact with anything around or below. Again it might just be ocd but I figured surfaces of any kind could increase/reduce read outs. On the left side of the space, just under canopy level I have a suspended hygrometer. On the right side also is the same. All tend to give similar temp read outs so I feel happy with that.. although I don't know if the placements themselves are still ''ok'' for cob/led, or if I am just following old hps philosophy. I also have the laboritory thermometer suspended in the room, it is above canopy hight but not in light range or direct air circulation. It reads about 4-5f higher than the other read outs but that seems about right given it's location, do suggest otherwise if not.
The humidity probe is placed next to the temp probe, centre canopy, but I have it just peaking above canopy. I have an under canopy extraction setup that sends lower humid air into the direction of the De-huey. The de-huey is sitting under a tower fan. The under canopy humid air and dry de-huey air basically gets mixed and pulled through the tower fan, then pushed over the canopy. The humidity probe then receives some of that mixed air to check if it's in range. The far left and far right hygrometers that are just under canopy tend to read up to 5% lower humidity than the center canopy rh probe. That makes sense given the locations/under canopy airflow but again, doesn't mean it's over all a good placement. I do wonder if it creates a kinda closed loop of the de-huey fighting respiration rates? or something like that.
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all it could possibly do was switch on at light out and off at light on when the temp got up.
) so there goes that theory ;p.
