Technischer Kundendienst
und Entwicklung
Norbert Gerhardt

Moisture Analysis

Electrolytic cell

TKE now has a brandnew set of tools for the determination of trace moisture in gases based on the coulometric technique. We offer an electrolytic cell, a data acquistion box and a free application software. Here is how it works:

The cell contains a ceramic strip with printed platinum electrodes. They are coated with a hygroscopic layer made of Phosphorus Pentoxide (P2O5) which attracts the water. In electrolytic cells the electric current is strictly proportional to the number of dissociated water molecules per time unit. This is an absolute measurement and requires no calibration.

While a sample gas streams through the cell at a typical rate of 100 ml/min, the current is measured with the acquisition box. This sensing technique is able to find single water molecules among a million gas molecules (ppm range). A water content of 1 ppmV (parts per million of the volume) corresponds to 13.14 µA.

Available in Q4 2020

TMM-1 Trace Moisture Meter

TMM-1 trace moisture meter with tablet

The TMM-1 Trace Moisture Meter is a universal gauge for the measurement of water in gases by the help of a Phosphorus Pentoxide (P₂O₅) electrolytic cell. Cells of most manufacturers can be used.

In standalone operation the TMM-1 shows the value on the front display and can put out a choice of signals via 4-20 mA current loop and relay contacts. After a power loss, the TMM-1 restores it's last state and continues to work automatically.
When hooked to a computer or tablet via USB, the TMM-1 can be fully configured through the Q-Moisture software provided by TKE. The control protocol and software are open source, hence users can make their own application.

The TMM-1 has a built in data logger. Logging starts and stops by the push of the rear panel button. When a computer is used for data capture, the logger will keep the acquisition going even if the computer shuts down or gets disconnected. Uninterrupted long time experiments become easy in this way.

Hardware Features

TMM-1 rear panel options

Rear Panel Choice

You can choose between two rear panel variants:

The laboratory panel has quick release clamps for the cell connection and a banana jack for grounding.

The industrial panel has pluggable Phoenixcontact terminals for the cell and power supply. The case grounding is a screw terminal.

Common to both rear panels is a DC jack for power supply, a USB Type B connector, an isolated 4-20 mA current loop outlet and two normally open (NO) relay contacts.

There is one pushbutton, which is used to toggle the display page and start / stop data logging.

TMM-1 printed circuit board

PCB Only Version

The TMM-1 Trace Moisture Meter is also available as printed circuit board without housing and with optional display.

If you plan to integrate the moisture meter into your OEM analyzer, you might only need the PCB. As an alternative to the USB jack there is an additional RS232 pin header for the communication with your local controller. A basic data protocol can be implemented according to your needs.

Power Supply Options

The TMM-1 Trace Moisture Meter can be powered through the DC jack with 5...24 V and via USB. Both inlets behave redundant, so continued operation is guaranteed while either one of the supplies fails. In the lab you can use a wall adapter, but in a fixed installation you might prefer a more reliable supply through the Phoenixcontact terminals. These are internally paralleled to the DC jack.

The power consumption is only 2.5 Watts at maximum cell load, typically 1 Watt. The unit therefore can be run from a 100 Wh USB power bank for several days.

TMM-1 with cell and power bank

Technical Specifications

  • Dimensions: H 52mm, W 90mm, D 113mm, Weight: 290g
  • Cell operating voltage: 0 ... 25.0 V in 0.1 V steps
  • Cell current limit: 0 ... 100 mA in 0.1 mA steps
  • Cell power limit: 1 Watt
  • Sampling interval: 1000 sec ... 1 kHz, 24 Bit ADC
  • Cell current accuracy: ±0.1% or ±0.01 ppmV @ 100 ml/min
  • Display resolution: 6 digits floating point

Q-Moisture Software

The Q-Moisture software is an easy setup and control tool for the TMM-1 Moisture Meter. It is used to prepare the TMM-1 for standalone operation in the field. In the laboratory Q-Moisture serves as plotter and control terminal. You can run and document experiments online or download and visualize data log files from the TMM-1.
The software is written in Python, so users are encouraged to add their own functionality or adopt the communication protocol in their own application.

Screenshot of Q-Moisture Software
Available in Q4 2020


  • Start / Stop data acquisition with live plotter.
  • Retrieve and display data log files from the TMM-1.
  • Export data to csv or txt file.
  • Set cell voltage, current limit, power limit, sampling rate.
  • Configure 4-20 mA signal source and scaling.
  • Configure relay signal sources and thresholds.
  • Setup the TMM-1 power on default behaviour.
  • Calibrate all analog circuitry of the TMM-1.

TKE Trace Moisture Cell

TKE P2O5 Trace moisture cell

This new P₂O₅ electrolytic cell developed by TKE is a cost saving and versatile solution for the measurement of water concentrations in gases down to 1 ppmV.

The cell can be opened, therefore the user can easily clean and regenerate it many times before a replacement becomes necessary.

The cell is also suitable for permanent installation in Ametek/Dupont analyzers as a replacement for the original Keidel cells. Ask TKE to convert your analyzer with the new cell, in case the Keidel cells should not be regeneratable any more.

TKE always holds fresh and tested cells on stock, so the user can swap the cell quickly in case of defects on the sensor strip.

TKE recommends to use the TMM-1 Trace moisture meter as it has enhanced protective features to keep the cell alive. However, the cell would also work well with third party equipment.

Opened TKE cell

Legacy Cell Regeneration

Keidel cells

TKE offers the regeneration of the phosphorus pentoxide moisture measuring cells (Keidel cells) that are used in the Dupont Moisture Evolution Analyzer MEA902/903 and the Ametek Moisture Monitor 303 as a special service.

In this process the cells are recoated according to the manufacturer's standard. As a result we restore 100% functionality. Of course, this does not apply to cells with internal glass crack or shortage between the platinum windings.

The regeneration service includes:

Moisture Analysis Expertise

Michell Instruments QMA401

TKE has gained years of experience in the development of trace moisture analysis solutions. If you need assistance in your project, we like to help where we can.

As one major project in the past TKE has developed an analyzer based on the Quartz Crystal Microbalance (QMB) technology. QMB works with an oscillating quartz disk that is coated with a hygroscopic polymer. When the coating absorbs water, the increased weight tunes the resonant frequency of the quartz to a lower value, which can be measured easily. This allows the determination of extremely small amounts of water down to 0.1 ppmV in gases. Compared to P₂O₅ cells, a broader range of gases is allowed to use as the polymer layer is unsusceptible to many substances.

We have submitted all rights for production and marketing of the QMB trace moisture analyzers to Michell Instruments Ltd. Learn more about this product here:

Moisture Analyzer Service

Dupont 303

We provide maintenance service for the moisture analyzers
Dupont 303, Ametek 303B, Dupont 902 / 903 and TA Instruments 903: