SSI Output: From Frame Structure to Master Implementation
SSI is synchronous serial: the master clocks, the sensor shifts out one bit per clock. Four wires look simple, and almost every failure sits in the timing detail of a single frame — the latch edge, the bit width, the code format, and the monoflop gap between reads. The articles below run from understanding the frame, through commissioning, to reading it on a master.
01Understand the frame first
- SSI Frame Structure: Clock, Bit Width and Gray Code
SSI uses four wires, yet one wrong setting scrambles every reading. A layer deeper than configuration: the four steps of a frame, why the width is only 25 or 24 bits, why neighbouring gray code values differ by one bit, and the arithmetic tying clock rate to cable length and update rate.
- Magnetostrictive Displacement Sensor Series 192: SSI Timing, Gray Code and Data Bits
SSI shifts position bit by bit, no bus stack. This magnetostrictive displacement sensor pairs cable length with baud, 48 μs gap, fixing Gray jumps.
- SSI Displacement Sensor 162 vs 192: Series 16 In-Cylinder Is Not Series 19
162 or 192 on an SSI displacement sensor? They share the D70 and 48 μs spacing—only mechanics differ; Series 16 keeps the 18G7 cap at 350/530 bar.
- SSI Displacement Sensor Wiring: Output Signals and How to Fix the Output at Selection
SSI is a synchronous serial digital output: clock plus data, no supply carried in the signal pair, and not a fieldbus. It can only be read by a PLC high-speed counter card or a dedicated SSI interface, and it cannot be converted to 4-20 mA or to a bus the way an analogue signal can. The right move is to fix the output type during selection — 4-20 mA or 0-10 V for an analogue input module, CANopen, Profibus-DP, EtherCAT or Profinet for a bus. The article ends with the correct four-wire 4-20 mA connection.
02Commissioning
- Debugging SSI: Waveforms, Bit Errors and Dropped Frames
SSI fails in only a few ways, and four of them separate cleanly on a scope: no communication, dead data, misaligned data, and occasional large jumps. This lays out the probe setup, the criteria and the order of checks.
- SSI Displacement Sensor Jumps After a Longer Cable: Drop the Clock to Match Length
Long SSI cable, then readings jump at rest? Drop the clock on an SSI displacement sensor: 1 MBd fits under 3 m; beyond 200 m it falls to 100 kBd.
- Magnetostrictive Displacement Sensor: Wiring Diagrams for All Series
Twenty wiring diagrams for magnetostrictive displacement sensors: Series 12 / 13 / 16 / 17 / 18 / 19 and the 7-pin D70 plug, covering analogue voltage and current (four-wire), Start/Stop, SSI, CANopen, Profibus-DP, EtherCAT and PROFINET. Pins are labelled P1–P7 with NC positions and cable colours, plus six wiring rules and a quick-reference table. Miswiring destroys the sensor.
- EtherCAT Real-Time: Distributed Clocks Align Instant, Not Measurement Speed
EtherCAT cannot break physics. DC aligns samples but cannot cut wave travel, so a longer-range magnetostrictive displacement sensor still runs slower.
03Getting it into a master
- Germanjet SSI Sensor Master: Modules and Bit-Banged Reads
SSI saves the protocol, not the implementation: you supply the clock, assemble the bits and keep the frame gap. Covers where the four master-side settings come from, how to fill in a PLC module, a GPIO bit-bang routine with three traps, and the time budget per frame.
- Turning Raw Position Counts into Millimetres in the PLC
The comms are up and the number moves, but it is an integer, not a distance. Conversion needs exactly three parameters: how many counts span the range, how far the zero is offset, and which way is positive. The difficulty is that the three live in three places - sensor firmware, program coefficients and the mechanical datum. Analogue, SSI, fieldbus and Start-Stop each hand over a different kind of raw value, so this article separates their conversion entry points and covers how to avoid throwing resolution away in integer arithmetic.
- Start-Stop Interface: Pulse Interval Converted to Position
Start-Stop magnetostrictive sensor pulses on the echo, so the controller times interval by wave speed. Simple wiring, but it needs a fast controller.
- Matching Sensor Output to the Controller's Available Channels
Analog, SSI or fieldbus? Pick this magnetostrictive displacement sensor by controller channels, axis count and diagnostics—matrix covers 191 to 199.
04Selection and comparison
- Magnetostrictive output signals compared: eight interfaces and their trade-offs
Eight outputs. A magnetostrictive displacement sensor differs by cores, noise, diagnostics: 4-20 mA cries open wire; 0-10 V reads break as zero.
- Magnetostrictive sensor outputs: 160 / 161 / 162, 180–185, 190–199
Before the PLC, decode the output code: Series 16 = 160/161/162, Series 18 = 180–185, Series 19 = 190–199. Watch for 162, Series 16 SSI, never 192.
- Magnetostrictive vs. Encoder: How to Choose for Linear Position Detection
A rotary encoder needs rack conversion and homing; this magnetostrictive displacement sensor reads the ring directly, no backlash, no homing.
- Magnetostrictive Displacement Sensor Series 197: EtherCAT State Machine and DC Clocks
The frame flies past; slaves read their bit. With DC synchronization, this EtherCAT displacement sensor suits multi-cylinder lifting; bus speed lags.