How can I calibrate my system with a microphone calibrator?

I would like to calibrate my microphones to dBSPL using a mic calibrator, inside of REW
I have a GRAS 45CA Ear Simulator that I am using to make headphone measurements. The device comes with a GRAS 42AA Pistonphone Microphone Calibrator, which produces 114 dBSPL (linear) at 250 Hz.
Before switching to REW, I was using the Audiomatica CLIO 12, which allows me to calibrate my microphone by setting a calibration level to expect, and then calculates a sensitivity by recording the signal when the calibrator is on and inserted over the microphone (See image below).

My question is, how can I do this within REW? My 1st thought is that my sensitivity will have to be in dBFS instead of dBV. I could perhaps measure the waveform when the calibrator is on with the Scope. I'm also not sure if I should make a cal file, because they appear to measure sensitivity w.r.t. 94 dBSPL.
My current rough calibration has been the standard method for room measurements using an SPL Meter and the replacement method.

My system is as follows: GRAS 45CA Left and Right Microphones -> Preamplifier -> Focusrite Scarlett 2i2 -> Thinkpad X1; Ubuntu 22.04.5 LTS; REW V5.31.3



Thanks for any guidance!

Follow the Calibrating the SPL reading help, selecting "External signal" at the relevant point and entering 114dB as the level.

Thanks, this solved it. My procedure for those wondering:

1. Open up the ear simulator to access the left microphone
2. In REW, under SPL Meter->Calibrate, set reference to 114dBSPL and hit start
3. turn on pistonphone and place over microphone
4. REW records measurement
5. Under Preferences->Mic Cal Files->Settings, REW has already calculated the dBFS @ 94dBSPL. Record this for future use (REW should save this value by default)
6. Repeat for Right Ear

tcoor8325 said:

REW should save this value by default

Click to expand...

The values are automatically saved as part of the cal data for that input. Make sure the option for separate cal for each input is selected.

tcoor8325 said:

Thanks, this solved it. My procedure for those wondering:

1. Open up the ear simulator to access the left microphone
2. In REW, under SPL Meter->Calibrate, set reference to 114dBSPL and hit start
3. turn on pistonphone and place over microphone
4. REW records measurement
5. Under Preferences->Mic Cal Files->Settings, REW has already calculated the dBFS @ 94dBSPL. Record this for future use (REW should save this value by default)
6. Repeat for Right Ear

Click to expand...

Thanks for the steps.