4.1 Setting of correction coefficient for other gases (only MASSFLOW 500)

4.2 Setting of the sensitivity of remote regulation (controller only)

 

4 VOLUME TOTALIZER

The MASSFLOW generates an electric signal after a delivery of each 5 ml of gas (for MASSFLOW 5000 range 0 to 5 l/min) or 0.5 ml (for MASSFLOW 500 range 0 to 500 ml/min). This signal can be accessed through the optional internal INTEGRATOR (art. no. 4803). The full range volume of the integrator is 327’680 ml (for the MASSFLOW 5000) and 32’500 ml (for the MASSFLOW 500). After this an automatic reset will set the integrator to zero and the integration will continue. In connection with a PC any volume from 5 ml (0.5 ml) upwards can be recorded (PNet, FNet or SIAM).

The MASSFLOW 500 high-sensitivity gas flow meter offers the possibility to measure small negative flows of gases (e.g. backflows). The RUN LED indicates a positive gas flow whereas the REMOTE LED indicates a negative gas flow. When the internal INTEGRATOR has been activated (optional), the corresponding INTEGRATOR pulses (corresponding to 0.5 ml each) are indicated by the blinking of the SET LED for positive gas flow and by the blinking of the ON LED for negative gas flow.

 

4.1 Setting of correction coefficient for other gases (only MASSFLOW 500)

MASSFLOW 5000 does not allow the setting of the correction coefficient for other gases. For the air-calibrated (standard) MASSFLOW 5000 oxygen as well as nitrogen can also be used. If another gas (e.g. for CO2) should be controlled or measured, a pre-calibrated MASSFLOW 5000 instrument should be used. Please contact us in this case.

MASSFLOW 500 can be used for measurements and control of flow rates of other gases. Because different gases have different heat capacities, a correction must be performed.

Let flow the new gas to assure that the MASSFLOW 500 sensor is completely filled with new gas. The setting of new correction coefficient (see correction factors in table 1) is done by the following procedure:

Make sure that there is no gas flow when performing the zero setting. Switch off the power supply. Press continuously the button RUN while connecting the power supply to mains. The message “NUL” will appear for one second on the display followed by the value of actual zero setting. Wait until the reading will stabilize and then press the button ON/OFF. The value will be set to the new zero corresponding to the gas used. The message “SLP” (slope) will appear on the display followed by the value of actual correction coefficient CFV (for air, nitrogen and oxygen it is 100, for CO2 it is 070 - this corresponds to CFV coefficient value 1 in Table 1). Set the coefficient corresponding to the new gas and press the button ON/OFF. The value of the new coefficient is saved and the MASSFLOW is ready for use.

The correction range of MASSFLOW is 001 to 185 corresponding to CFV values of 0.01 to 1.85 (see Table 1).

The correction coefficient will affect the measurement range. For the correction coefficient 100 (air, oxygen, nitrogen) the range corresponds to 0 to 500 ml/min. For the correction coefficient 070 (carbon dioxide CO2) the range is reduced correspondingly to 0 to 350 ml/min.
It is not possible to measure exactly helium and hydrogen, because of their very different properties. If only less precise flow rate value indication is required, leave the setting for nitrogen and divide the displayed value by 10 to obtain the real flow rates with these gases. The regulation will proceed normally. For precise measurements of these gases it is preferable to use instruments calibrated for these gases.

Table 1: Correction factors CFV and CFM at 23°C for calibration with N2.

Gas

Factor CFV for Normalized Volume Flow

Factor CFM for Mass Flow

N2

1

1

O2

0.992

1.14

Air dry

0.998

1.026

Air 100% relative humidity

0.996

1.017

CO2

0.70

1.10

CH4

0.90

0.51

C2H6

0.48

0.52

C3H8

0.32

0.51

Ar

1.27

1.80

He

ca. 9

ca. 1.3

H2

ca. 10

ca. 0.6

 

4.2 Setting of the sensitivity of remote regulation (controller only)

In certain situations, especially for cell cultures with low volume of medium, the use of the full range of flow rates is not required but much finer regulation is needed. For this use the MASSFLOW is equipped by sensitivity adjustment in the range 0 to 100 %.

Switch off the power supply. Press continuously the button Λ used for setting hundreds digit under the display while connecting the power supply to mains. The message “Att” (attenuation) will appear for one second on the display followed by the value of actual sensitivity/attenuation value. Select the required attenuation value (for example 50 for the sensitivity reduction to one half or 10 for ten times reduced sensitivity). The maximum flow rate value will decrease correspondingly and the regulation of e.g. dissolved oxygen or pH will be smoother.

Remark: The value 000 is identical to 100 %.