EBME Forums Forums Maintenance Service Manuals & Schematics Respical T300 gasflow analyzer, who is still using

This T300 analyzer，Cannot display zero position.
I have checked the sensor and the op amp circuit and found no faults.
I don't know how to adjust it.

If you know how to adjust please let me know, thanks

I believe you need the software (and connect to a PC) in order to re-calibrate and reset to zero.

You probably need a new oxygen sensor, as well.

Have you hounded down the software yet?

Yes, I have not found the software,I disassembled the main unit and checked the circuit board.
Below are some pictures I took apart, hoping to give me repair suggestions

I checked the data sheet of the sensor,VCC is 5V power supply,vout is the analog output voltage.
For example,0 cmh2o=2.92v,10cmh2o=3.15v,20cmh2o=3.38v,30cmh2o=3.61v.........0.2xV voltage increase.The highest I chose 4.92V, the pressure reached 85.07cmh2o.

But the low pressure range can only reach 85.07cmh2o，The instructions say that it can reach +-120cmh20,I do not know why
Low pressure can reach as low as -128.05cmh2o,I think this is normal

I am at the pressure sensor voltage output interface,Use a separate power supply to connect the voltage.
View the pressure value on the screen and record the corresponding voltage value
But why the pressure value can only reach 85.07cmh20and 85.44psi?
According to the manual, it should be +120cmh2o and 100psid

After 6 months of testing, I finally finished the calibration of the T300 analyzer, thank you friends for your help