Use this table to help diagnose a fault with your Series 900 or 930 handheld monitor.
If you’re unable to find the fault in the table, or the suggested fix doesn’t work, email support@aeroqual.com.
| Fault | Possible causes | Solutions |
|---|---|---|
| No power | Power connection broken Power supply failure Monitor damaged | Reconnect power cable Replace 24 VDC plug pack Replace monitor |
| RS485 communications unstable | RS485/RS232 adaptor faulty Connections broken ID incorrect Noise on cable Sensor head not fitted correctly | Reconfigure/replace adaptor Reconnect leads Check ID Use shielded twisted pair cable Insert head correctly |
| 4-20mA output failure | 30V input exceeded | Replace monitor |
| Network unstable | ID conflict Noise on cable Jumpers set incorrectly Monitors are too close together | Modify IDs so that no S900 or S930 monitors share the same ID Use shielded twisted pair cable Set jumpers correctly The cables between the monitors should be a minimum of 30 cm in length |
| If connected to a display, display shows -1 | Over-range (>20mA) reverse loop current | Loop polarity is incorrect. Reverse the polarity. Incorrect loop polarity can cause irreversible damage to the monitor |
| If connected to a display, display shows 1 | Over-range loop current (>20 mA) | Reduce loop current |
| If connected to a display, display shows -.125 | 4-20mA loop not powered | IPower loop. The display requires the loop to be powered to read correctly |
| If connected to a display, display oscillated between min and max | Sensor head not fitted correctly | Insert sensor correctly |
| Sensor failure when new sensor connected | Insufficient warm-up Air contaminated Sensor damaged | Run the sensor for 24-48 hours Move the sensor to cleaner environment and check reading Replace sensor |
| Sensor showing high baseline reading under zero gas conditions | Background gas level higher than normal Interference gas present Sensor zero drift Sensor damaged | Move sensor to clean environment and recheck baseline Move sensor to clean environment and recheck baseline Rezero sensor in a clean, stable environment Replace sensor |
| Sensor showing higher than expected reading in the presence of sensor gas | Zero calibration incorrect Span calibration incorrect Interference gas present Sensor calibration lost | Zero calibrate sensor Span calibrate sensor Move sensor to clean environment and check reading upon exposure to know concentration of gas Replace sensor |
| Sensor showing lower than expected reading in the presence of sensor gas | Zero calibration incorrect Span calibration incorrect Sensor inlet contaminated Interference gas present Gas reactive and decomposing before detection Sensor calibration lost | Zero calibrate sensor Span calibrate sensor Clean sensor inlet filter and mesh Move sensor to clean environment and check reading upon exposure to know concentration of gas Move the monitor closer to the source of the gas Replace sensor |
| Sensor output noisy | Monitor power supply unregulated Local air flow too high Environmental conditions fluctuating | Install regulated power supply Reduce air flow Reduce fluctuations |
Diagnostics
Series 900 and 930 monitors have inbuilt diagnostics to detect sensor faults. If the sensor fails, it can be easily replaced by removing and installing a new sensor head. The failed sensor can be sent back to Aeroqual for replacement or disposal.
| Fault | DIAG output | 4-20mA output | RS485 output |
|---|---|---|---|
| No fault | Floating | Valid gas reading | Valid gas reading Status 1 = 0x00 |
| Sensor failure | GND | 20mA | Last valid gas reading Status 1 = 0x01 |
| Sensor aging | GND | 20mA | Last valid gas reading Status 1 = 0x02 |
| Sensor not fitted correctly | GND | Oscillated between 4 and 20mA | No reply |