CHAPTER 1
(cont)
TELEVAC
Theory of Operation:
The MC300 is a microprocessor-controlled instrument utilizing modern data acquisition
techniques to achieve a high degree of accuracy at a reasonable cost.
The microprocessor in the instrument performs two basic tasks:
1. Controls the acquisition and conversion of all sensor data
2. Processes all operator interface inputs and requests
After power is applied to the instrument, the software initializes all of the circuitry
associated with acquiring and displaying sensor information then performs a self-
diagnostic. If there are no errors detected, the MC300’s data acquisition process is
started. Both input channels are read periodically and a reading for each sensor is stored.
After several readings the data is averaged, then converted using the appropriate sensor,
units and gas compensation settings. Set point relays and the microprocessor controlled
Analog outputs are also updated at the same time. This method of averaging samples
results in a smooth and accurate transition from reading to reading.
Each sensor has its own conversion algorithm. The data conversion process always
occurs regardless of the instrument mode (operation set-up). However, during the set-up
mode the converted data is not sent to the display but the set-point relay control and
analog output operations continue to operate.
Whenever the instrument software is not processing sensor data for the displays or
recorder outputs, the Set-Up, Test/Operate and Up & Down (if enabled) buttons are
checked for operator interaction. The Set-Up button is used to sequence through all of the
operator settable parameters. Each depression of the Set-Up button may change the
function of the displays as well as the Up & Down buttons. Each time the Set-Up button
is pressed, the data from the previous level is stored in non-volatile memory to ensure
that the instrument’s gas compensation, units and set point parameters are preserved. This
information is used to restore the instrument’s configuration each time power is applied.
For simplicity, the Up & Down buttons are enabled and disabled at the proper time to
prevent the operator from entering an invalid value. In addition, each time an On Point is
adjusted, the corresponding Off point is verified to ensure that it is higher then the new
On Point. If lower, the Off Point is adjusted to be one increment higher than the new On
Point. In this instance both the On and the Off Point values are updated in the non-
volatile memory.
When “GAS” is selected in SETUP, a correction is applied to the instrument readings to
compensate for the use of Argon as a gas instead of nitrogen/air. Both the displayed
readings and the set point calibrations are compensated as well as the linear thermocouple
and the linear by decade convection gauge recorder outputs at the back panel. Note,
however, that the “traditional” thermocouple, “linear” convection gauge outputs and ion
gauge outputs are NOT compensated.
Phone:(215) 947-2500 fax:(215) 947-7464 e-mail: [email protected] web site:www.televac.com
6-8000-002 REV A
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