BUCHI ELS Detector C-650 - Manual (Page 35)

C-650 Operation Manual, Version B 5 Putting into operation 35
When the detector is powered up or if you change the temperature, the temperature may first
overshoot the setpoint slightly and then stabilize at the desired point. This initial overshoot is due
to the regulation of the device and should not be a concern.
Provide gas to the detector and adjust the pressure to 2 bar (29 psi). If the pressure is less than
1,5 bar (21 psi), the pressure value blinks, indicating that the detector is not ready.
Make certain that the pressure of gas supplied to the detector is less that 4.5 bar (67 psi). If the
pressure increases above 4.5 bar (67 psi), the pressure sensor may be damaged. This damage
is not covered by the warranty.
If you have an external gas gauge, make sure that the external reading and the reading on the
Status screen are the same.
Press the „ZERO“ button. The signal should be close to zero and remain constant.
Set the noise filtering to 1 second (refer to Fig 5.18).
5.9.2 Electronic noise test
To determine the electronic noise:
Do not switch the light source on. Do not switch the pump on (no solvent flow).
Make sure that the siphon is filled and the nebulizer inlet connector is blocked with Parafilm TM to
avoid a Venturi effect.
Set gas pressure to 2 bar (29 psi) and temperature to 50 °C. Wait for stable temperature.
Set gain 12 and monitor the signal for a period of 5 min. The variation in the signal should be less
than +/-2 mV (there may be some spiking of the signal).
Record the level and autozero the detector again.
5.9.3 Background noise (stray light) test
To determine the background noise:
Do not turn on the pump (no solvent flow).
Make sure that the siphon is filled and the nebulizer inlet connector is blocked with Parafilm TM to
avoid a Venturi effect.
Set gas pressure to 2 bar (29 psi) and temperature to 50 °C.
Switch on the light source.
Change the Gain to 1.
Set the offset to 0 mV.
Set the offset after Autozero to 0 mV (refer to Fig 5.17).
Autozero the detector.
Change the Gain to 12.
Wait 15 minutes for stabilization and record the signal level. The expected level is typically 100 mV
to 150 mV. The exact value will vary slightly and small deviations should not be a cause for con-
cern.