Salt test for multiple hygrometers?

[MajorCaptSilly]

I have 6 hygrometers with wide-varying readings. I'm doing the salt test with all of them in a sealed tupperware container and large ziplock bag. I used a shot glass with the distilled water/salt mixture. The shot glass is only 1/4 full. My question is will this be good enough to get an accurate reading on all 6 hygrometers or should I do 1 at a time?

Thanks,

MCS