Recalibrating the Lip Strength Meter

Hi, I wondered if you know of a way to recalibrate the lip meter.  My gauge is not zeroing for me and I have to adjust to what I think the reading is.  Can you shed some light on this? Thanks so much!  

Although the Lip Strength Meter has been a worthy piece of equipment for me and for 1000s of others worldwide, I am happy to let you know that there is now a friendlier creation known as the Myo Lip Meter.  It was developed by an engineering company so that therapists could have a lighter, more scientifically up-to-date tool that was more reliable and consistent.  It fits comfortably in the hand and is less likely to set off a red flag through airport security, as well!  To view how it looks and works, click the following links: https://orofacialmyology.com/myo-media/ https://orofacialmyology.com/shop/lip-strength-meter/