Electrochemical Sensor
Analytical sensing instruments utilizing a selective membrane function as the primary tool for determining hydrogen ion activity in wet finishing baths. The glass electrode operates by establishing an electrical potential across a thin, pH-sensitive glass membrane that separates the process solution from an internal reference solution. This potential varies linearly with the logarithm of the hydrogen ion concentration, providing a continuous voltage output.
For textile dyeing operations, this voltage is translated directly into a pH reading.
Potential Measurement
Achieving accurate measurements requires the glass electrode to remain free from surface contamination by dyes and sizing agents. When these processing chemicals deposit onto the outer surface, they form a barrier that slows down the ion exchange between the glass and the textile bath. The result is a sluggish response or a drifted reading that can ruin a batch of dyed fabric by causing inconsistent shade matching.
Regular chemical cleaning with dilute acid or mild solvents is necessary to restore the active surface of the membrane. This maintenance schedule directly affects the reliability of automated dosing systems in high-capacity continuous dye ranges, where a small measurement drift can lead to hundreds of meters of off-shade material before the error is caught.
Sodium Error
High sodium concentration in concentrated mercerizing baths causes a specific measurement discrepancy when using the glass electrode. At pH values above twelve, the thin glass membrane begins to respond to sodium ions instead of hydrogen ions. This effect makes the solution appear less alkaline than it actually is, which can lead to over-dosing of caustic soda.
Specialized high-pH electrodes are used to minimize this error.
Process Calibration
Industrial dyehouse environments subject the glass electrode to harsh chemical environments that demand frequent verification. Operators perform two-point calibrations using standardized buffer solutions to adjust for temperature effects and electrode aging. Because textile processes often run at elevated temperatures, automatic temperature compensation is integrated into the transmitter.
This ensures that the calculated pH reflects the true chemical state of the bath during operation.
