Teledyne 9110T Watchdog Circuitry, Valve Control, Yellow no 2  no Converter Heater

Model 9110T NOx Analyzer Principles of Operation

D10 (Green) – NO/NOx Valve

D9 (Green) – AutoZero Valve

D8 (Green) – Optional Sample/Cal Valve

D7 (Green) – Optional Zero/Span Valve

D3	(Yellow) NO2  NO Converter Heater
D2	(Yellow) Reaction Cell Heater

D5 (Yellow) – Optional Internal Span Gas Gen Heater

D11 (Green) – Optional Dual Span Select Valve

D12 (Green) – Optional Pressurized Span Shutoff Valve

D13 (Green) – Optional Pressurized Zero Shutoff Valve

D1 (RED)

Watchdog Indicator

Figure 13-17: Status LED Locations – Relay PCA

13.3.4.2. Watchdog Circuitry

The most important of the status LED’s on the relay board is the red I2C bus watch-dog LED. It is controlled directly by the analyzer’s CPU over the I2C bus. Special circuitry on the relay PCA watches the status of D1. Should this LED ever stay ON or OFF for 30 seconds, indicating that the CPU or I2C bus has stopped functioning, this Watchdog Circuit automatically shuts all valves and turns off all heaters.

13.3.4.3. Valve Control

The relay board also hosts two valve driver chips, each of which can drive up four valves. The main valve assembly in the 9110T is the NO/NOX - Auto-zero solenoid valve component mounted right in front of the NO2 converter housing (see Figure 3-5).

∙These two valves are actuated with 12 V supplied from the relay board and under the control of the CPU through the I2C bus.

Additional valve sets also controlled by the CPU via the I2C bus and the relay PCA can be included in the 9110T (see Table 1-1 and Sections 3.3.2.3, 3.3.2.4, and 3.3.2.5 for descriptions of these valve sets).

Teledyne Analytical Instruments 348