How to Read a Medical Oxygen Sensor Datasheet
When replacing a medical oxygen sensor, you need to check its datasheet to find oxygen sensor specifications such as output, response time, and operating life. To read the datasheet correctly, check each value with its test conditions, then compare it with the requirements in your equipment’s instructions for use (IFU).
This guide will show you what every line on a medical oxygen sensor datasheet means, using the M-01 datasheet below as the example.
Medical Sensor Datasheet Example
What Is a Medical Oxygen Sensor Datasheet?
A medical oxygen sensor datasheet is the manufacturer’s specification sheet for one sensor model. It lists the sensor’s performance along with how the sensor should be stored before use. On most NRC Pure sensor datasheets, the specifications are grouped into three sections:
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Key feature: the main specifications and their reference conditions.
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Storage conditions: temperature, humidity, and shelf life before installation.
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Related products: part numbers for each version of the sensor.
A quick datasheet check will usually tell you if a replacement works. If you're not sure which model you need, check out our guide on finding compatible oxygen sensors for your device.
How to Read a Medical Oxygen Sensor Datasheet
Read the datasheet from top to bottom, matching each numbered section with the image to the explanation below.
1. Sensor Type and Key Feature
The top of the datasheet identifies the sensor type and model. In this case, the sensor is an M-01 medical oxygen sensor. The key feature line below it summarizes the design. The M-01 is a single-cathode sensor, which means it has one measuring electrode and sends one output signal to the equipment. Some medical sensors are dual-cathode and send two separate signals, so the number of cathodes should match your current sensor.
The rest of the line describes stable output, low interference from anesthesia gases, and good linearity across the full measurement range. Treat this line as a summary. Use the specifications in sections 10 and 11 to verify the sensor’s performance against your equipment’s requirements.
2. Reference Conditions, Units, and Symbols
Reference conditions are the temperature, humidity, and air pressure under which a sensor’s specifications were measured. On the M-01 datasheet, they appear below the key feature line as 25°C, 50% relative humidity (RH), and 1013 hectopascals (hPa), which is standard sea-level air pressure. Every value on the sheet was measured under these conditions unless its own line states something different, such as “@ dry ambient air” or “applied for 5 min.”
The datasheet also uses a few units and symbols that change how a value reads:
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Vol.% is the share of a gas, by volume, that is oxygen, so room air is about 21 Vol.% O2.
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% rel. is a percentage of the current reading, not of the whole 0 to 100% scale
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@ means “measured at” the condition that follows.
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< and > mean less than and more than, ≤ means at most, and ± gives the allowed range on either side of a value.
3. Measurement Range
The measurement range is the span of oxygen concentrations the sensor is designed to read. The M-01 covers 0 to 100 Vol.%, from no oxygen at all to pure oxygen. Many medical oxygen sensors share this range.
4. Expected Operating Life and Sensor Lifetime
Expected operating life is the total oxygen exposure a sensor is rated to handle, stated in Vol.% hours. It is calculated by multiplying the oxygen concentration by the hours of exposure. The M-01 lists more than 500,000 Vol.% hours.
Sensor lifetime is a separate limit in years. The M-01 lists less than three years in ambient air, depending on the application. Plan replacements around whichever of the two limits your equipment reaches first.
5. Electrical Connector
The electrical connector line tells you how the sensor connects to the equipment. The M-01 uses gold-plated slip rings, which are flat metal rings on one end of the sensor that touch matching contacts in the equipment. The gold plating resists corrosion, which could otherwise weaken the sensor’s small millivolt signal. Other medical sensors use connectors such as 3.5 mm jacks, Molex connectors, or wired leads, so a replacement’s connector has to match the one on your current sensor.
Read more: Medical Oxygen Sensor Connector Types
6. Initial Output Signal
The initial output signal is the signal a new sensor produces in dry room air. Medical oxygen sensors send this signal as a voltage, measured in millivolts (mV), or as a current, usually measured in microamps (µA). The M-01 produces 14.0 to 20.0 mV, which makes it a voltage-output sensor.
The “load 300 Ohm” note at the end of this line means the output was measured across a 300-ohm resistor. The sensor’s voltage depends on that resistance, so a different load would change the voltage measured at the equipment’s input. For a replacement, the output type, the output range, and the load should all match your current sensor, or the equipment may fail to calibrate.
7. Response Time (T90)
Response time (T90) is how long the sensor takes to reach 90% of its final reading after the oxygen concentration changes. The M-01 reaches it in less than 17 seconds. The last 10% of a galvanic sensor’s response is slow, so manufacturers measure to 90% to give a figure that can be compared between sensors.
T90 affects how quickly the oxygen display and alarms respond when the oxygen concentration changes. Check that the value is the same as or shorter than your current sensor’s. Keep in mind that the value was measured at the 25°C reference temperature, and a colder sensor usually responds more slowly.
8. Drift
Drift is how much the sensor’s reading shifts over time while the oxygen concentration stays the same. The M-01 lists less than 1 Vol.% O2 per month in air, averaged across 12 months. For example, a sensor reading 20.9 Vol.% in room air would drift by less than 1 Vol.% per month on average if it isn’t recalibrated.
“Averaged across 12 months” means the figure is a yearly average, so a single month can drift more or less than 1 Vol.%. Drift is one of the reasons equipment requires regular calibration, and a sensor that drifts less may hold its calibration longer between checks.
9. Operating Temperature and Pressure Range
The operating temperature is the range the sensor is designed to work in once installed. The M-01 operates between 10 and 40°C, so check that this range covers the temperature where the sensor sits inside your equipment. If you’re storing a spare sensor, follow the storage limits in section 13, which differ from the operating range.
The pressure range is the span of gas pressures at which the sensor is designed to measure oxygen. The M-01 lists a range of 700 to 1250 hPa. The sensor responds to oxygen partial pressure, so a pressure change shifts its reading even when the oxygen percentage stays the same.
10. Linearity Error, Zero Offset Voltage, and Repeatability
These three specifications describe how accurate the sensor’s reading is. Each was measured after the test gas had been applied for five minutes, so the reading had time to settle.
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Linearity error: How far the output strays from a straight line between zero and full oxygen. The M-01 stays within 3% at 100% oxygen. This matters because some devices calibrate in room air and calculate higher readings from that point.
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Zero offset voltage: The reading the sensor gives in pure nitrogen, when no oxygen is present. The M-01 states it as an oxygen reading instead of in volts, at no more than 0.3 Vol.% O2. It matters most when the equipment measures low oxygen concentrations.
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Repeatability: How closely the sensor gives the same reading when it measures the same gas again. The M-01 stays within ±1 Vol.% O2 at 100% oxygen.
When you compare these values with your current sensor’s datasheet, check that both were measured with the same test gas and exposure time. A figure measured at 100% oxygen can’t be compared directly with one measured in air.
11. Influence of Humidity and Interferences
Influence of humidity shows how much the reading changes as humidity changes. The M-01 lists −0.03% rel. O2 reading per % RH, which means the reading drops by 0.03% of itself for every percentage point of extra relative humidity.
Interferences show how other gases in the mix affect the oxygen reading. The M-01 refers to DIN EN ISO 80601-2-55, the international standard for respiratory gas monitors, and its key feature line describes low cross-interference to anesthesia gases. If the sensor goes into an anesthesia workstation, check that its datasheet states interference performance the same way your current sensor’s does.
12. Weight and Material in Contact With Media
The M-01 weighs approximately 20 grams.
Material in contact with media lists the materials that the measured gas touches, since “media” here means the gas. For the M-01, these are PA (polyamide), PPS (polyphenylene sulfide), PTFE (polytetrafluoroethylene), and stainless steel. The list helps when you need to check the sensor against the gases used in your equipment. For cleaning, follow the sensor and equipment manufacturers’ instructions.
13. Storage Conditions and Shelf Life
Storage conditions are the limits for keeping the sensor before it’s installed. The M-01’s recommended storage temperature is 5 to 30°C, and its maximum range of −20 to 50°C is allowed for no more than 10 hours. Storage humidity can reach 100% RH as long as it’s non-condensing, meaning no water droplets form on the sensor.
The recommended shelf life is less than six months, so plan to install the sensor within that time. Ordering replacements close to when you need them keeps stock from sitting past this limit.
14. Related Products and Part Numbers
The related products section lists the versions of the sensor with their own part number. The M-01 comes in four versions, with white or translucent housings and other differences listed in the “Other Specifics” column. When you order, match the full part number to your current sensor, because versions of the same model can differ in housing and other details.
Compare Your Replacement Line by Line
A datasheet is most useful when you read it next to your current sensor’s datasheet, one line at a time. At NRC Pure, we match each of our medical oxygen sensors to specific equipment models, and each one comes with a specification sheet like the M-01’s.
Search for your equipment in our compatibility list to find its matching sensor and datasheet. If your equipment or a matching sensor isn’t listed, send us your equipment’s manufacturer, model, and specifications, along with details of the sensor it currently uses. We’ll find a matching sensor for you.
Frequently Asked Questions
Where Can I Find the Datasheet for My Current Oxygen Sensor?
Start with the model and part number printed on the sensor’s label. The sensor manufacturer or supplier usually publishes the datasheet under that model. If the label is unreadable, the equipment’s service manual or IFU names the specified sensor.
Why Do Oxygen Sensor Datasheets From Different Manufacturers Look Different?
Manufacturers don’t follow one shared layout, so the same specification can appear under different names and units. Units can even vary between sheets from the same manufacturer, with zero offset given in microvolts on one sheet and in Vol.% O2 on another. Match each value by what it measures and how it was tested, not by its label.
Does a Sensor’s Output Still Match Its Datasheet After Months of Use?
No. The datasheet lists the initial output of a new sensor, and that output falls gradually as the sensor ages. The equipment’s calibration adjusts for the drop until the output is too low to calibrate, which is usually when the sensor needs replacing.
