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THEORY OF OPERATION M300EU
Addendum to M300E/EM Manual P/N 04288
10.3.2.3. Status LED’s
This information replaces that found in Sections 10.4.5.5 of the M300E/EM Operators Manual.
• Eight LED’s are located on the analyzer’s relay board to show the current status on the various control
functions performed by the relay board (see Figure 10-14 of the M300E/EM Operators Manual).
• They are:
Table 10-2: Relay Board Status LED’s
LED COLOR FUNCTION STATUS WHEN LIT STATUS WHEN DARK
D1
RED Watchdog Circuit
Cycles On/Off Every 3 Seconds under direct control of the
analyzer’s CPU.
D2
YELLOW Wheel Heater HEATING NOT HEATING
D3
YELLOW Bench Heater HEATING NOT HEATING
D4 YELLOW Oven Heaters HEATING NOT HEATING
D5
GREEN
Sample/Cal Gas
Valve Option
Valve Open to
CAL GAS FLOW
Valve Open to
SAMPLE GAS FLOW
D6
GREEN
Zero/Span Gas
Valve Option
Valve Open to
SPAN GAS FLOW
Valve Open to
ZERO GAS FLOW
D7
GREEN
Shutoff Valve
Option
Valve Open to
CAL GAS FLOW
Valve CLOSED to
CAL GAS FLOW
D8
GREEN IR SOURCE Source ON Source OFF
10.3.3. MOTHERBOARD
The information found in Section 10.4.6 of the M300E/EM Operators Manual (P/N 04288) is applicable to the
M300EU with the following additions:
10.3.3.1. A to D Conversion
Because the M300EU has much higher resolution and sensitivity than the M300E/EM, the possibility that
temperature-coefficient related drift could occur in the 10.3.3.1. A to D conversion circuitry if there were a
significant difference in temperature between the converter and the surrounding airspace. To prevent this, a fan
direct heated air directly onto the A to D converter area of the motherboard to ensure that it is as close as
possible to the current temperature of the oven area.
10.3.3.2. Sensor Inputs
OVEN TEMPERATURE SENSOR
A thermistor is located in the center of the insulated oven area (see Figure 3-1). It measures the analyzer’s
inside temperature. This information is stored by the CPU and can be viewed by the user for troubleshooting
purposes via the front panel display by selecting the test function OVEN TEMP or reported via the instruments
TEST CHANNEL analog output (A4) by setting the output function also named OVEN TEMP.
56 05831 Rev. 01