Siemens RAPIDLAB 248, Operator'S Manual, Page: 48 / 135

Page 3-10 248 Operator’s Manual
Checking the Gas Pressure and Changing the Cylinders
Checking the Gas Pressure
1. Check the main cylinder and second stage pressure.
Figure 3-6. Checking the Gas Pressure
The main cylinder pressure must be higher than 300 psi. The
second stage pressure must be 4
±
1 psi.
2. If the main pressure is less than 300 psi, check that the cylinder
valve is open. If it is and the pressure is low, the cylinder is empty.
Change the cylinder.
Changing the Cylinders
CAUTION:
The instructions given are for Siemens gas cylinders and
regulators and we recommend the use of these at all times. If you use
other cylinders and regulators they must meet the following
specfication:
• Only certified value gas cylinders should be used.
For calibration gas the value should be 5% CO
2
(acceptable range
4 to 6%) and 12% O
2
(acceptable range 10 to 14%), balance N
2
.
For slope gas the value should be 10% CO
2
(acceptable range 8 to
12%) and 0% O
2
(acceptable range 0 to 2%), balance N
2
.
The gas values used must be entered (see Section 5, Configuring the
System ).
• The regulator must have a low diffusion diaphragm to prevent
selective diffusion and alteration of the gas values. All fittings must
be leak free. The regulator must have a low flow precision needle
valve for gas flow adjustment and supply 4
±
1 psi at a flow of up to
20 cc/minute. When the needle valve is closed the output psi must
not rise by more than 2 psi compared to the ‘open’ output.
• The tubing used must not allow selective diffusion of CO
2
, O
2
or N
2
.
Siemens tubing is designed to maximize through-flow rates,
reducing the diffusion rates. The accuracy of the 248 is adversely
affected by the use of diffusive tubing.
• Siemens assumes no liability for performance when non-standard
equipment is used.
Second Stage
Pressure Gauge
Main Cylinder
Pressure Gauge