Technical Note: Rig Tension Sensor series of Dead-Eyes

Strain Measurement Devices, a world leader in thin film strain gages, introduces the world’s most highly engineered group of Dead Eye and Rig Tension Sensors.   Using our sensor and strain gauge design experience SMD crafted a sensor and circuit that is designed to measure tension accurately in a sailing rig by adding a custom thin film strain gage sensor  into an Aluminum 6061 deadeye with a wireless circuit.  Testing each design iteration and measure performances of individual mechanical designs or machined features, makes this the highest engineered Dead-Eye available.  This Patent Pending Design uses unique machining features that allow the rigging lines to run with minimum stress concentrations and  improve Hysteresis in the system, also offering a waterproof, wireless and solar powered system. 

Two ranges of dead-eyes are available currently to suit either the 15-17 mm or 11-13 mm Dynema. The former having a safe working load of 25 Kpounds and the smaller at 15 Kpounds.

Mechanical Accuracy of the Sensors are defined as the sum of Non-repeatability, Non-Linearity and Hysteresis. Non-Repeatability and Non-Linearity are typically better than 1%, while Hysteresis is rigging line dependent and can contribute up to a 5% for full load excursion.


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Sensor Mechanical
Non Repeat-ability   0.2% FSO
Non-Linearity  0.7% FSO
Hysteresis: Line Dependent   1-6% FSO


Thermal Errors
Temp. Co of Offset (TCO)   +/- 0.01 FSO/C
Temp. Co of Span (TCS)   + 0.03% FSO/C*
*Typical, Improved TCS available  


Bluetooth   Unpaired
Update Rate   100 Millisecond
Battery Life   No solar charge available: 28 Days
Solar Panel  Full recharge in 30 mins, full sun
Range  50′ line of sight
Hermetic On/Off rotary switch included for known down times
Mechanical Details 
15-17 Dynema Dead Eye   25,000 lbf Safe Working
 50,000 lbf Breaking Strength 
 5/16″ [8 mm] Lashing Line
11-13 mm Dead Eye   15,000 lbf Safe Working
 30,000 lbf Breaking Strength
 1/4″ [6.4 mm] Lashing Line

O’ring sealed to IP67