What Is The Difference Between An SSI And An SPI Displacement Sensor?

Selecting a displacement sensor for automation raises a question as to what is the difference between SSI and SPI displacement sensors. An SSI serves as a differential while being non-multiplexed and actively simple, while pertinently relying on the data’s time-out frame. The SPI is duplex and actively uses a chip to frame the data. 

Both of these key terms display themselves often in the SSI  and SPI displacement sensor, specifically when the draw-wire encoders make use of the packaging lines or even heavy machinery or AGV. With Briter Encoder, we offer the space to make significant progress by matching the right sensor to your core controller and wiring layout.

Table of Contents

• Is SSI or SPI better for displacement sensors?
• How are SSI and SPI wired differently?
• Does SSI or SPI give better accuracy?
• Which one should I choose, SSI or SPI sensor?

Is SSI or SPI better for displacement sensors?

When drawing a significant question, such as which communication protocol is better for displacement sensors, SSI or SPI, the better choice when you draw a line of difference between the SSI and SPI relies on your key system setup. You can choose tSI for the core industrial ecology and even for the applications that demand high immunity to noise. On the other hand, you can actively choose the SPI for short-range communications, where the transmission of high-speed data is critical.

How are SSI and SPI wired differently?

At Briter Encoder, our SSI displacement sensor and SPI displacement sensor are wired differently because the SPI is primarily bidirectional and multi-device. Here are the factors that are considered

• SSI Wiring: A set of differential data pairs and a clock that assist the runs of 100+meters while tolerating the electrical noise through RS-422/485 signaling
• SPI Wiring: Involving four single-ended lines, such as tOSI, followed by MISO, and simultaneously functions best under a few meters and requires shielded wiring to prevent any loss of signal

Whereas the SSI is actively unidirectional and known for being point-to-point.

Does SSI or SPI give better accuracy?

When you draw a distinction between the SSI and the SPI for the sensors and the key encoders, neither of the protocols can be determined as being inherently more accurate than the other one. At Briter Encoder, we believe that the prior accuracy is determined by core resolution and the respective internal encoder design, which is actively measured in bits, such as 12-bit or 10-bit, over the protocol. 

Further, the differential signal, which is characterized by the SSI, assists in the idea of maintaining data integrity over long and noisy cable runs, which thus indirectly safeguards accuracy within the harsh ecology. Whereas the SPI can deliver a much more precise set of headings. However, precision matters only when the cable length is short and the shielding is properly managed. Noise will corrupt single-ended signals over distance.

Which one should I choose, SSI or SPI sensor?

Choosing between the SSI and SPI sensors primarily comes down to your system’s physical layout and the controlled hardware. However, at Briter Encoder, we offer you:

• Choose the SSI
  You can choose SSI for simpler wiring than multiple SPI slaves and for higher-precision applications, which are primarily implemented with absolute encoders and simplex communication that drives unidirectional data transmission.
  
  Also Read: (Incremental VS Absolute Encoders Principles · Differences · Advantages · Application Insights)
  
• Choose the SPI
  You can choose the SPI if you want an ideal on-board usage for shorter distances between the localized sensor and microcontroller. Further, you can use the SPI for direct MCU assistance, wherein native hardware support is ubiquitous across microcontrollers.
  
  The prior ideas to consider, besides whatever you choose, are flexibility, feasibility, and what is required for immediacy.

Summary

The core displacement sensors, namely the SSI and the SPI, offer absolute position data. However, they fit in varied working conditions. The SSI feels much more rugged and is suited to long-distance industrial setups. Whereas the SPI primarily fits within a compact and even shorter range of electronic integrations. At Briter Encoder, we manufacture these precision draw wire encoders, designed to handle challenging environments, whether you work with construction equipment or packaging machinery.

Are you ready to look for the right sensors for your system? Explore our sensor product range and contact us via email at brt@briterencoder.com to receive even better guidance from our team today. Ultimately, our sensors are built to deliver durability and accurate absolute position sensing.

FAQs

1. Is it possible to convert an SSI sensor to an SPI output?
   No, SSI and SPI sensors use different signal timing and voltage levels, so you need to determine the correct protocol before installation.
   
2. How long can you use a cable length with an SSI sensor and an SPI sensor?
   Differential signaling allows for an SSI to be used with cable lengths over 100 meters, while SPI has a cable length of only a few meters before the signal degrades.
   
3. Are the supply voltages for SSI and SPI sensors the same?
   Often yes. In most cases, both use supply voltages of 5-30 V DC; however, there is some variation by model, so it is always a good idea to check the datasheet before making any assumptions based on the protocol.