Tin Bath Atmosphere Oxygen Sensor

Opening sidewallThe Read-Ox tin bath atmosphere sensor, for measuring the oxygen activity of the protective atmosphere in the tin bath, is very sensitive to even the smallest amounts of oxygen leaking into the bath atmosphere. It is an ideal tool for indicating when sealing improvement activities are required or when an increase of the venting intensity and/or hydrogen supply to the bath is needed. Moreover, the sensor provides immediately feedback on the effectiveness of a specific sealing action.

Using the atmosphere sensor, the log(pO2(bar)) and the log (pH2O/pH2) of the protective atmosphere can be monitored. The pH2O/H2 buffer controls the oxygen activity of the protective atmosphere and is a good measure for the reducing or oxidising effect of the atmosphere on the tin melt, independent of the bath’ temperature.

installation atmosphere sensor 684x553

The atmosphere oxygen sensor can be easily installed in a side wall guide tube, similar to the installation of a regular tin bath thermocouple or a tin melt oxygen sensor. The only difference is that the measuring tip is positioned above the tin melt in the protective atmosphere, whereas the measuring tip of a thermocouple of a tin melt oxygen sensor is positioned inside the tin melt.  The large aluminium terminal head provides much space for convenient connection of the signal cables (t/c mV-signal and oxygen cell mV-signal) to the IOSI signal converter.

By measuring both the oxygen activity in tin and in the protective atmosphere in one particular bay, the driving force for tin melt deoxidation can be monitored for optimal oxygen removal in various sections of the bath.


Two types of tin bath atmosphere oxygen sensors are supplied:

  • Standard sensor for mid bath and hot end section of the bath (application range 650 to 1000ºC)
  • Cold end atmosphere sensor: with sensitive oxygen cell for relatively low temperatures (application range 550 to 650ºC)

Driving force for tin melt deoxidation

Under normal production conditions, the oxygen activity of the protective atmosphere is lower than that of the tin melt for an effective removal of oxygen from the tin melt. In this way the oxygen content of the tin melt can be kept low enough for defect free production. As most of the tin melt surface is covered by the glass ribbon, oxygen is more or less entrapped in the tin melt under the glass ribbon. Oxygen removal is a slow process, which can only take place via the small open space near the side walls of the bath.

Figure Oxygen Cycle

Control scheme

For this reason it is important to measure both the oxygen content of the tin melt and that of the atmosphere in various sections of the bath in order to maintain enough driving force for tin melt deoxidation along the entire length of the bath.

A detailed study on the behaviour of oxygen in the tin bath and the use of tin oxygen and atmosphere oxygen sensor pairs along the tin bath from hot end to cold end can be found in: Glass technol.: Eur. J. Glass Sic. Technol. A, December 2012, 53 (6), 261-272. This study was performed by the Asahi Glass Production Technology Center, using Read-Ox' tin bath oxygen sensors.

Signal converter

Read-Ox provides a DIN rail mountable oxygen sensor interface (READOX IOSI-01). This signal converter was specially developed for Read-Ox' oxygen sensors. The tin bath atmosphere oxygen sensors give out an oxygen cell mV-signal and a thermocouple type K mV-signal, which are converted by the IOSI-01 interface to three analog 4..20 mA outputs. The standard settings are:

For the standard tin bath atmosphere oxygen sensor:

  • I-out1: Temperature of the protective atmosphere: 4..20 mA = 0..1200 (ºC)
  • I-out2: Log (pO2) of the protective atmosphere: 4..20 mA = -40..-10 (-)
  • I-out3: Log (pH2O/pH2) of the protective atmosphere: 4..20 mA = -4..2 (-)


The output calculations and ranges may also be (re)programmed through the IOSI's USB port by using the specially develloped PC software package ImOxyConfig. In this way the end user can configure the IOSI-01 according to his specific wishes. For a detailed specification of the oxygen sensor interface please click here...