how to measure temp in vacuum chamber/BHO extraction?

When measuring the temperature with an IR temp gun, I should be measuring the BHO puddle itself right? But how do I measure it while its purging?i can't through the top glass. I am going to be putting the vacuum chamber on a griddle.
What do i do? Do I stop the pump and halt purging, and open the vacuum chamber- take the temp then close and resume purging? I would think I would have to do this frequently to get the temp dialed in. Is it counterproductive to keep stopping luring to open it up to measure temp?
Where and how should I measure the temp?

Here is what I do... I got my griddle turned on but below the lowest temp reading, then I have a skillet of water that my purge chamber sits in... the water temp usually is 110 degrees which will get my oil to 80 degrees.... also I have the parchment paper with the wax during on a plastic vented tray, do it doesn't sit right on the purge chamber... those numbers took me sometime to dial in but work for me.... but I really do suggest using a pan with water because griddle alone will be to hot....

A griddle is too hot; even on low. You only need to get it to about 90deg F to purge under vac & you don't want it to go over much over 100. I used to use a small heater pad like you would use for a sore back & just take the fabric cover off exposing the plastic. I wrap the heater pad around the mason jar I use as vac chamber & turn my vac pump on to purge. A double boiler type setup is the only way to use a griddle without burning your errl but it's overkill imo. You only need to warm it up enough to release the butane under vac - 90 deg or so is plenty- used to purge a few g in a matter of hours

I am new to bho but I use a griddle too and keep the temps around 120 deg. I'll check and dial in the temp by opening the vac chamber. It also will hold the vacuum so I close the valve and power it off between checks. I'll also play with it when I check the temp, squeeze it between the silicone pads and mash it around. It's a lot of fun!