What’s the Cost of Inaccurate Humidity Measurement?

During recent projects with a leading compressed air product and solution manufacturers, an interesting query was posed: what effect would inaccurate humidity-moisture measurement have on energy consumption and cost? A calculation taking into account pressure dewpoint, flow, running hours per year, dryer load, and energy unit cost provided an interesting insight.

Inaccurate measurement in compressed air

Compressed air systems are measured and controlled with dew-point sensors. ISO 8573 is the compressed air standard which defines dew point and other limits; Class 1 specifies a maximum of -70 °C dew point (< 3 ppmV H₂O at atmospheric pressure).

At -70 °C dew point, the calculation* identified that a 5 °C dew point inaccuracy would cost €5228 per year for a single dry compressed air system. Multiply that by the many compressed air systems on-site and throughout industry, and that can become a significant waste of money and resources.

Compromised Quality and Yield could be even more costly in other industries

In many other applications, inaccurate humidity-moisture measurement can directly affect the bottom line.

For example, in semiconductor production, the tiniest moisture ingress can contribute to defects, reliability issues, yield loss, and a lower-grade product. If humidity-moisture sensors are inaccurate or drying systems fail in wafer fabrication facilities, manufacturers may experience increased defect rates, yield losses, and reduced production efficiency.

In battery manufacturing, moisture contamination can cause cell failure and thermal runaway, leading to safety incidents in electric vehicles, bicycles and manufacturing plants.

If failures are not catastrophic and do not affect safety or the product directly, inefficiencies can go unnoticed and subprocesses remain suboptimal.

So, the cost of inaccurate humidity measurements can lead to direct and indirect costs that can be substantial.

Reducing the risk – finding an alternative strategy

Numerous industrial processes use humidity-moisture sensors to monitor and control water content; to maintain that measurement performance, calibration is generally carried out on a regular schedule. 

Calibration frequency depends on the type of instrument and the criticality of the measurement, but is typically six or 12 months.  This usually requires the sensor to be uninstalled and sent back to the supplier or manufacturer.  So, engineering, change control, and logistics costs can be significant.

This strategy also requires process plants to hold stocks of spare sensors to provide measurement continuity while sensors are away being calibrated, further escalating costs.

It’s no surprise that many users are looking for alternative strategies to maintain or improve measurement performance and save costs.

Moving towards onsite calibration

Qrometric’s FPG Dew-Frost point calibrator is a breakthrough solution that enables manufacturers and process plants to calibrate sensors on-site.

The FPG’s portable benchtop design enables on-site use in production lines, factory environments, workshops, and laboratories. It generates a stable frost point by recirculating the sample gas through a temperature-controlled saturator until thermodynamic equilibrium is reached. Under these conditions, the frost point is defined by the saturator temperature, providing a stable reference for sensor calibration and validation. The FPG can be used as a standalone calibration system or in combination with a transfer standard for enhanced confidence/lower uncertainties.

On-site calibration means that instead of sending hundreds of sensors away each year for calibration, only those that need repair or readjustment need be returned. This advantage removes many hours of downtime, reduces the required backup sensor stock levels, and enables significant cost savings related to the consequences of inaccurate sensors.

A recent cost benefit analysis at a battery production site with fifty dew point sensors concluded that the FPG return on investment was little over a year based only on the cost to calibrate the sensors.

* Example based on:

300 L/s compressor, PSA dryer type  
Running hours per year: 5500
Energy cost: 0.2 €/kWh
Load of the machine: 100% PSA dryer, -70 °C PDP¹