An electrochemical oxygen analyzer measures oxygen with a cell that is consumed as it reacts. An optical analyzer measures it without that cell. In natural gas service the practical differences are what has to be replaced, how H₂S and CO₂ affect the sensor, and how often someone has to visit the site.
An electrochemical or galvanic cell generates a current as oxygen reacts at an electrode. The cell is consumed as it works, so its life is finite: it depends on how much oxygen the cell sees and on the gas around it, and the cell has to be replaced on a schedule.
An optical oxygen analyzer reads oxygen with a fully optical sensor instead of an electrochemical reaction. For OxyScout, that means there is no electrochemical cell to replace. The outputs are 4–20 mA and RS-485 Modbus RTU.
| Factor | Electrochemical (galvanic) cell | Optical (OxyScout) |
|---|---|---|
| What wears out | The electrolyte and electrode are used up, and the cell is replaced on a schedule. | No electrochemical cell has to be replaced. |
| H₂S and CO₂ | H₂S can poison cells, and CO₂ can react with some electrolytes. | OxyScout has no cross-sensitivity or poisoning from H₂S, CO₂ or the other gases that plague galvanic cells. |
| Site visits | A cell change needs a visit to the site. | There is no scheduled cell swap. |
| Price positioning | The initial purchase price is similar to OxyScout. | OxyScout is priced comparably to electrochemical analyzers. |
For a single analyzer at an easy-to-reach site on clean, sweet gas, the lifetime difference may be modest. If you run many remote sites, cell changes and truck rolls add up, so count them. Decide on your own site count, gas and visit costs, not on a general rule.
Purchase price is only one line of the total. To compare two analyzers fairly, pick one service life of N years, the same for both, and add up each of the following cost lines for the whole period. Do the sum for your own sites rather than relying on a generic figure:
Total cost over N years equals the purchase price, plus the sensor changes times the part cost, plus the site visits times the cost per visit, plus the calibration gas, plus the cost of bad data. For an optical analyzer, count any Sensor Cap changes your sites actually make. For a cell, use the replacement interval your own sites see.
Tell us your cell replacement interval, part cost and cost per site visit, and we can build a side-by-side for your sites. Book a quote meeting to start.
Read the optical oxygen analyzer specifications, or see where oxygen enters in the applications.
No. An optical analyzer has no electrochemical cell to replace.
H₂S can poison electrochemical cells. OxyScout has no cross-sensitivity or poisoning of the optical sensor from H₂S, CO₂ or the other gases that plague galvanic cells.
OxyScout is priced comparably to electrochemical analyzers.
Count the purchase price, the sensor replacements, the site visits, the calibration gas and consumables, and the cost of bad data.
You might stay with one at an easy-to-reach site with a single analyzer on clean gas, where the difference may be small.
Book a 30-minute meeting to review your application and we'll send you a quote after the call.
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