Through experiments to determine the amount of active ingredients in the drug solution consumed per unit of electricity (Ah) (such as g/Ah). Example: For every 1000Ah consumed, 5L of concentrated phosphate solution needs to be replenished to maintain the concentration. Proportioning factor (K): K = Make-up volume (L or g) Cumulative Ah K= Cumulative Ah Make-up volume (L or g)
How to control the concentration of pharmaceuticals through ampere-hour meter equipment
Author: Robby
Controlling the concentration of pharmaceutical solutions (e.g. phosphating solutions, plating solutions, etc.) during phosphating or other electrochemical treatments by means of Ampere-hour meter (Ah) equipment is a precise management method based on power consumption. The core principle is to indirectly reflect the consumption of active ingredients in the liquid by monitoring the accumulated power (Ampere-hour, Ah), so as to automatically replenish the chemicals or adjust the process parameters. The following are the specific realisation methods and steps:
1. Ampere-hour meter working principle
Ampere hours (Ah) = current (A) × time (h), that is, the unit of electricity.
Assumptions: the consumption of active ingredients in the liquid and the amount of electricity (Ah) into a linear relationship (need to experimentally verify the proportionality coefficient).
Control logic: when the accumulated power reaches the set value, trigger the refill system (such as pumps, valves) to add concentrated liquid or supplements.
2. System components
Ampere-hour meter: real-time monitoring and totalising the product of current and time (Ah).
Current Sensor: Measures the actual current in the process tank.
PLC/Controller: Receives Ah data, compares it to a preset threshold, and triggers a refill action.
Refill device: such as metering pumps, automatic dosing system.
3. Steps for controlling the concentration of drug solution
(1) Establish the concentration - power relationship
Experimental calibration:
Through experiments to determine the amount of active ingredients in the drug solution consumed per unit of electricity (Ah) (such as g/Ah). Example:
For every 1000Ah consumed, 5L of concentrated phosphate solution needs to be replenished to maintain the concentration.
Proportioning factor (K):
K
=
Make-up volume (L or g)
Cumulative Ah
K=
Cumulative Ah
Make-up volume (L or g)
(2) Setting Ampere-hour meter parameters
Enter the calibrated scale factor (K) to the PLC or controller.
Set the replenishment threshold (e.g., replenish every 500Ah accumulated).
(3) Automatic Top-Up Control
When the accumulated Ah reaches the threshold value, the controller starts the refill pump and adds the liquid according to the K value.
Example:
Current accumulated Ah: 500Ah → refill volume = 500 × K = 2.5L concentrate.
(4) Feedback calibration (optional)
Regularly take samples to check the actual concentration, compare it with the theoretical value, and correct the proportion coefficient K.
4. Key Notes
Initial calibration accuracy: The K value must be determined through several experiments to avoid over or under replenishment.
Current fluctuation processing: If the process current is unstable, dynamic integral calculation (real-time Ah accumulation) is required.
Compatibility of the components of the liquid: only applicable to the components whose consumption is directly related to the power (e.g., Zn²⁺, PO₄³-, etc. in the phosphating solution).
Temperature/pH influence: If the concentration is influenced by other factors (e.g. temperature), it needs to be combined with the sensor for comprehensive control.
5. Application Scenarios
Phosphate solution maintenance: control the concentration of Zn, Mn, Ni and other metal ions.
Plating solution management: replenish metal ions of plating layer (such as Cu²⁺, Cr⁶⁺).
Wastewater treatment: precise flocculant dosage (needs to be combined with ORP/pH sensor).
6 Advantages and limitations
Advantages:
High degree of automation, reducing the frequency of manual testing.
Avoid process defects caused by concentration fluctuations (e.g. uneven phosphate film).
Limitations:
Periodic calibration of K-values is required, especially when the liquid is aged.
Not applicable to non-electrochemically consumable components (e.g. volatiles).
7. Extended programme (advanced control)
Multi-parameter linkage: combined with pH meter, hydrometer, etc. to improve control accuracy.
Data logging: Record Ah and refill history through SCADA system to optimise the process.
Controlling the concentration of drug solution through Ampere-hour meter is essentially using power consumption as an indirect indicator of process stability, which is suitable for large-scale continuous production scenarios. Practical applications require the adjustment of parameters according to the specific composition of the liquid and process characteristics.