Factors Causing Instability of the Detection System in Infrared Carbon & Sulfur

The detection system acts as the core heart of the carbon-sulfur analyzer. Stable baseline output of the detection system is critical for reliable test results. However, multiple factors can trigger system instability, imposing high technical requirements on operators and maintenance personnel. Analyzing these unstable factors is of great significance for equipment maintenance and ensuring smooth scientific research workflows. For years, unstable detection performance has remained a common trouble for instrument users. Long-term research and equipment maintenance have accumulated valuable practical experience, which helps boost equipment utilization, guarantee on-time completion of research and production tasks, and standardize routine maintenance of infrared carbon-sulfur analyzers.

The measured signal intensity is closely correlated with the working power supply output, infrared source radiant power, chopper motor frequency, infrared detector, A/D analog-to-digital converter, and external interference. Root causes for unstable system performance are categorized as follows:

1. Aging of electronic components causes unstable output and excessive ripple voltage. Normal power supply fluctuation tolerance is ±10%; readings exceeding this range indicate abnormal status.
2. Damaged components lead to zero output or distorted waveform signals. Faulty parts can be identified by measuring voltage at key circuit nodes and comparing with standard nominal values.
3. 
   

1. Gradual aging of the light source reduces radiant output and lowers signal amplitude. Baseline values of carbon and sulfur detectors will drop continuously, triggering instrument alarms once readings fall below the normal range.
2. Broken or desoldered heating filaments cut off signal output entirely. Verify the filament resistance (standard value approx. 5 Ω) for troubleshooting.
3. Cold solder joints or oxidized power plugs create poor contact. Variable contact resistance leads to drastic random fluctuations of output signals, a frequently overlooked failure mode.
4. 
   

1. Motor stall: either power supply failure or mechanical jamming of the chopper blade assembly.
2. Long-term mechanical wear enlarges shaft sleeve clearance, causing unstable blade rotation. Blades may collide with the detection cell wall and become stuck.
3. Deviation of the motor’s modulation frequency from nominal values leads to uneven light transmission through the aperture, resulting in fluctuating or zero received signals at the detector.
4. 
   

1. Complete component damage with zero signal output.
2. Aging reduces sensitivity and introduces high noise floor in output signals.
3. Oxidized solder joints and cold solder connections cause unstable signal transmission.
4. 
   

1. Degraded performance of the micro-signal amplifier; prioritize checking filter capacitors and grounding integrity during inspection.
2. Poor contact of zero-adjustment and gain potentiometers. Rotate potentiometers back and forth several times regularly to restore good contact.
3. Degraded amplification gain of the quad operational amplifier leads to low final analytical readings.
4. 
   

1. Aging components on the A/D board degrade performance, increase interference noise and scramble digital signals.
2. Poor instrument grounding introduces external electromagnetic interference, resulting in missing sampled data.
3. Loose contact between the A/D board and bus slot causes loss of collected test data.
4. 
   

Analysis of these instability factors provides effective solutions for common faults including aged electronic components, degraded performance, zero/unstable signal output, excessive noise, missing or lost sampling data. Resolving these issues greatly improves equipment utilization efficiency and guarantees stable long-term operation of infrared carbon & sulfur analyzers.