Sensirion’s SDP5xx sensors reach the end of production
Illustrative image: Unsplash contributor on Pexels
Sensirion is due to stop production of four SDP5xx pressure sensors on 26 October 2026, which is also the final delivery date in its discontinuation notice. Orders under the published last time buy arrangement closed on 26 July, so October marks the end of that schedule rather than a fresh opportunity to order.
The company has identified specific SDP6xx replacements that it describes as drop-in devices sharing the mechanical and electronic design. It also recommends the SDP800 series for longer term supply security, although that involves a different I²C command set. The replacement decision consequently reaches into the firmware as well as the component list.
| Discontinued sensor | Specified SDP6xx replacement | Replacement order number |
|---|---|---|
| SDP500-500Pa | SDP600-500Pa | 1-100456-02 |
| SDP501 | SDP601-500Pa | 1-100603-02 |
| SDP510-500Pa | SDP610-500Pa | 1-100455-02 |
| SDP511 | SDP611-500Pa | 1-100604-02 |
The notice, issued on 26 January, describes consolidation of the portfolio. Its recommendation of SDP800 for future supply does not specify a guaranteed number of years of availability.
There are reasons for preserving the exact variant in that discussion. Within the older family, SDP50x and SDP60x devices connect to a manifold, while SDP51x and SDP61x have ports for tubes. The SDP501/511 and SDP601/611 versions also use temperature compensation intended for mass flow measurement, rather than the compensation used by the corresponding differential pressure versions.
They still report differential pressure. The compensation is adapted for an installation where the pressure reading is used to determine flow, which is why matching the pressure range and housing would leave part of the specification unresolved.
Sensirion’s measurement guide describes how that installation works. A restriction in the main gas path creates a pressure difference, with the sensor connected across it in a bypass. A small gas flow passes through the sensor’s thermal measuring element. The relationship between the pressure reading and the main flow depends on the system’s design and characterisation; there is no universal conversion from pascals to litres per minute.
The software changes with SDP8xx
The older SDP5xx/SDP6xx datasheet specifies a default seven-bit I²C address of 0x40 and an eight-bit measurement command, 0xF1. The digital SDP800/810 devices use address 0x25, while SDP801/811 use 0x26. Commands on the newer digital platform are 16 bits long.
An existing driver that continues sending the old address and command would therefore not perform the documented measurement transaction for the replacement. Sensirion’s own driver documentation identifies incorrect address selection as a cause of unanswered requests and NACK errors.
The newer digital family also provides a choice between continuous measurements and measurements triggered individually. Its triggered modes distinguish mass flow from differential pressure compensation and include options for clock stretching. The returned data can include pressure, temperature and a pressure scale factor, arranged as 16-bit words with checksum bytes.
That changes what the host sends, when it expects a response and how it reads the result. A firmware update would have to account for the chosen measurement mode and timing, including the effect on any control loop using the readings. Receiving a plausible pressure value once would demonstrate less than operating the revised sensor correctly through start-up, normal measurements and recovery from communication errors.
Some details do carry across. For the relevant 500Pa digital versions, both datasheets specify a pressure scale factor of 60 counts per pascal. A correctly decoded signed result of 6,000 therefore represents 6,000 ÷ 60 = 100Pa. The arithmetic stays familiar even though the transaction used to obtain the value changes.
The electrical specifications also warrant a separate comparison. The older platform operates from 3.0–3.6V, while the digital SDP8xx range is 2.7–5.5V. Those figures describe the sensor supply; they do not by themselves establish compatibility with every existing arrangement of bus pull-ups, wiring and host electronics.
The pneumatic connection remains specific to the model. In the newer family, SDP80x devices connect to a manifold and SDP81x devices provide tube connections. Sensirion also offers analogue SDP800 family devices, which are outside this digital interface comparison.
