getting acurate temp readings inside cab ?

[bdomina]

hello again!

What is the best way of taking temps from within your cab. Right now I have a 400 HPS w DIY cool tube. Air pulled through using stanley blower. it gets about 10* above room temp. right now it is setting at about 83 -85. but the tube is warm at best. you can totally handle it without flinching. I am thinking that wherever my temp node is, that it is getting some kind of direct light reading and possibly throwing it off. it is sitting on top of the aerotub. the flower cab is about 2dx3wx4h. ballast is outside cab, flower chanber is the better part of a large closetmaid type cab from home depot...any rules of thumb in getting an accurate temp?

thanks.
~BD~

 

[Blue Dot]

...any rules of thumb in getting an accurate temp?

I don't think a lot of people know this or ever really thought about it but did you know that when you read the temps in your daily newspaper around the county that those temps are always in the SHADE.

If your newspaper says it was 100 degrees they mean it was 100 degress in the shade. It would obviously be much warmer in the sun.

 

[KUSHEATER1]

set it in the shade of the ladies

 

[bdomina]

right on. thanx for the replies. no shrubbery in therejust yet. making sure everything is good before i pop these mp5k's i have. for now i guess i will improvise and either put something that will throw a little shade in there or put the node down in between the res and the side , somewhere out of the direct light....i think i might be good. I do not have the cash for an AC unit but i DO have a tstat and a compressor from a freezer i gutted. anyone know how i can make that work for me by chance?

 

[thc43]

High

I might be able to assist i recently changed the shape from rectangle to L shape Gr and find below a decent way of getting average temps and or sorting hot spots.

many Digi thermo readings would be the best way to set you growrooms up. Hang the things everywhere. go FkN nuts cant have too many, batteries last for ages most probes work in water or go the 50cent aquarium numbers.

The Oscilating fan is a good way to move air around reasonably well in a small to med GR, if airflow through the room is emptying total space every few minutes you have a perfect enviroment 90% of the year where i live ( land of the Quakka)

hot spots in GRs need to be found and delt with. Often a bubble of heat directly under globes in corners up high in room go not noticed increasing overall GR temp (off reading). If sorted you can move on knowing your venting is sorted till next up/down size.


1x digi temp guage to read outside airtemp(probe) unit in the bedroom/shed/attic or where Grow box is situated.

2nd and third digi gauge in the grow room itself measuring canopy level/ soil temp(probe) at exhaust end of room and guage 3 at canopy with probe hanging off my centre of 3 lights 1/2 between globe and canopy. Lets me know whats going on where and how to angle lower moving fans. $16 do the job fine

In my room i used this multi guage guide to first setup my room. movement within the GR is as if not more important to total cfm per sec/min flowing through per mimute.

Not dispersing hot spots or stagnent air can end in pain powdery mildew in wetter months, stretchy bud in areas of heat maby even radiation burn. digi and cheep aquarium type thermometers do the job buy more than needed om in the res, mother pot so on they go fast. each room will be different generally good to over venting an oscirlating fan per light upto 4 maby more lights should work in most parts of the world.

Its well worth sorting sooner than later easiest without plants in the room OC, then corrected again as canopy fills up.

time 4thc43

 

[nut]

put your thermometer just above the reflctor so the light does not shine on it, but dot hang it directly above above the reflctor hang it a foot or so to the side of it. that will give you a better ambient air temperature reading.

 

[sparkjumper]

I love using my lazer thermometer from taking canopy and ambient temps to temps inside the humidity dome.The Fluke 62 mini IR thermometer is really nice and inexpensive.No more guessing

 

[Blue Dot]

I love using my lazer thermometer from taking canopy and ambient temps to temps inside the humidity dome.The Fluke 62 mini IR thermometer is really nice and inexpensive.No more guessing

How can it measure ambient temp (room temperature) when a room is mainly composed of air and a laser thermometer only measures temps of surfaces?

Surfaces heat and cool much differently then air.

 

[hoosierdaddy]

acu-rite w/ remote sensor.
walmart, bLowes, home dePot, et al...

 

[YosemiteSam]

How can it measure ambient temp (room temperature) when a room is mainly composed of air and a laser thermometer only measures temps of surfaces?

Surfaces heat and cool much differently then air.

True...but it is the surface temps of the leaves that really matters...so measure those and then make the necessary adjustments to achieve the leaf temps you want.

 

[nut]

True...but it is the surface temps of the leaves that really matters...so measure those and then make the necessary adjustments to achieve the leaf temps you want.

ambient room temps is what you want to go by, to see how low you can get the light = radiant heat just put your hand above the plant if it feels hot you need to move it higher. the radiant heat from the ambient heat in the room are 2 differant things. think of the sun on a hot summer day it feels hot and you will burn, but if you sit in the shade you feel hot, but you dont burn. plants can take more radiant heat than ambient heat. i.e for the leaf to be 75f a 1000w light would need to be 6 foot away we know we can get the light closer to the plant than that. the ambient heat in the room will make the plant drink more water faster that can slow or speed the plant growth up or down anything over 90f without co2 will slow plant growth down without co2 75-80f ambient room temps are the best for plant health and growth rates.

 

[nut]

In order to know you are providing the right thermal environment for you plants through ventilation, oscillating fans etc. you need to understand the physical nature of the 'heat' in grow spaces, how it should be measured, and the mistakes that can easily be made.

Essentially there are two aspects to the thermal environment that you need to be aware of:

1. The AIR temperature
2. The RADIANT temperature

Although obviously related, these are 2 distinctly separate phenomena and your plants have different tolerances for each.

1. Air temperature
Your standard mercury/alcohol-bulb or digital thermometer is designed to measure the temperature of the air (But not radiant heat). This is what is being referred to in the usual growers 'rules of thumb' such as maintaining your grow above 16degC and below 30degC.

Most thermometers are only designed to measure air temperature – growers often mistakenly place their thermometer in direct light; radiant energy will warm your thermometer and give a higher than actual reading.

*Assuming your air is well mixed up by oscillating fans, it doesn’t really matter where you locate your thermometer. The best spot is probably about half the way up a wall, with a piece of cardboard over it (To shade it from radiant heat), exposed to the mixed air in the grow room.

2. Radiant temperature
Radiant temperature is the result of heat transfer bewteen objects at different temperatures without whats inbetween i.e. the air, being effected. In our case the plants are naturally at a lower temperature that the light and reflector so heat is transferred to the plants foliage from the light/refecltor through radiation. This causes the leaves to heat up. The plants can withstand much higher radiant temperatures (around 40-50degC) than they can air temperatures but if this is too high the plants can 'burn'.

The plants can withstand much higher radiant temperatures than they can air temperatures, but if this is too high the plants can “burn”.

'The hand test': Place your hand in a comfortable position for some time at the tips of your plants should be. If your hand feels “hot”, then the lights are too close, the radiant energy is too intense, and light burn may result. Do this test and raise your HID lights/reflectors periodically to keep light burn to a minimum.

Finally, monitor the conditions in your grow regularly as things are changing all the time, and you will soon get to understand the thermal dynamics of your particular grow space so you can get the most from it.

Editor’s note:
[Cannabis loves high light levels/high radiant energy levels, but exceeding their tolerance for light can result in light burn and chlorophyll leaching out of the leaves. 600's & 1000’s put out a lot of light, and light burn can easily damage clones and young plants.

Light burn damage: initially the leaves look pale green (the edges may turn upwards, mimicking a Mg deficiency), then they turn yellow and finally yellow/brown as the leaves scorch.

Often you can see a circular pattern of intense light where the reflector has focused the light onto the plants. If plants outside of this intense light zone look greener and healthier, consider raising your lights.]