Super Systems MGA6000 - Manual (Page 10)

SSi Manual #4563 Rev. D Page 10 Multi-Gas Model 6000
• Temperature Units = This determines the measurement units for temperature. Enter 0 for
Fahrenheit (degrees F) or 1 for Celsius (degrees C).
Although it is possible to enter the data manually using the keypad, the atmosphere controller should be
utilized to provide the data automatically if possible. When the data is entered automatically, it will change
as the composition of the atmosphere changes. This will allow for a more reasonable correlation between
the values from the MGA and the values from the probe.
The probe information can also be used to ensure that the pump operates only when the conditions are right
for sampling. This can be used to prevent damage to the instrument if the pump is left running as the
furnace cools or when the conditions deviate from pre-determined parameters. For additional information on
operating the pump in “Auto Sample” mode, please refer to the section titled
Sampling Parameters (menu
option 17).
Measurement of Infrared % Carbon (IR %C)
To accurately measure the % carbon in a furnace atmosphere, the instrument will need to know the values
of CO, CO2, and CH4 and the temperature of the gas being measured. At the left side of the screen, under
the heading
Measured , are the real-time values of CO, CO2, and CH4. The values of these three gases, plus
the furnace temperature (FC TC) value, will result in the calculation of the IR % Carbon (IR %C). This is
displayed in the center of the screen, under the heading
Calculated . Please note that if the furnace
temperature information has not been entered correctly the resulting carbon calculation will not be accurate.
For best results, it is recommended that the temperature information be entered automatically from either
the atmosphere controller or the temperature controller.
Measurement of Probe % Carbon (PB %C)
The measurement of the probe % carbon requires three pieces of information to be entered. These are the
probe millivolts (PB MV), probe temperature (PB TC), and either the COF or the PF (depending on the type
of atmosphere controller you are using). The probe millivolts and probe temperatures are entered on the
right side of the page, under the heading
Operator . Before entering either a COF or a PF, you will need to
determine the manufacturer of the atmosphere control instrument you are using. If SSi, Honeywell, Barber
Colman, Yokogawa, or anyone other than Marathon Sensors manufactures the instrument, then it will
contain a CO Factor (COF) adjustment variable. If the user is using a Marathon Sensors instrument, then
this variable is called a Process Factor (PF) adjustment. Only one of these (COF or PF) will be used at any
one time, and the other will not be relevant. If the instrument has a CO Factor adjustment variable, then
use the up or down arrow keys to go to the appropriate field and type in the value that is stored in your
atmosphere control instrument. After the value is entered, an asterisk (*) will appear next to the number.
This lets the user know that the CO Factor is being used for the calculations, not the Process Factor. If the
instrument has a Process Factor adjustment variable, then this value should be entered in the “PF =” slot,
which will result in the asterisk appearing by that number entered.
The calculation of probe % carbon is no different from the % carbon as displayed on the atmosphere
controller. The algorithm used by both instruments in their calculations is identical. The reason the
information is entered into the MGA is not to calculate the probe % carbon, but to enable the MGA to
compute the suggested COF / PF. Without knowing the current instrument values, it cannot compute the
suggested values.
What is a CO Factor or a Process Factor?
The carbon probe is measuring the amount of oxygen in the atmosphere. Knowing the amount of oxygen,
the atmosphere controller can determine the percentage of carbon. The calculation that the instrument uses
to translate oxygen concentration into percent carbon is based on a theoretically pure atmosphere being
present in the furnace. The composition of this theoretically pure atmosphere is 40% hydrogen (H2), 40%