DKFB Strain Ring Gauge for Round Tie Bars

Strain measured on a round tie bar without glue and without calibration: the ring clamps around the bar with two screws and presses foil strain gauges, protected under a stainless steel foil, against the surface so firmly that friction carries the surface strain into the gauges.

It replaces the bonding a strain gauge otherwise needs, and with it the three quarters of an hour, the chemical cleaning and the grinding – the measuring location only has to be free of loose material such as rust or flaking paint, and a solvent is enough. It works on any round bar, magnetic or not.

Measurement

• Reads the surface strain of the bar directly, like a bonded gauge
• Range ± 1000 µε, accuracy and linearity each < ± 0.5 % of full scale
• Hysteresis < ± 0.2 %, repeatability < ± 0.1 %
• Foil gauge, GF = 2.0, 350 Ω bridge – usable without a calibration of its own
• Sensitivity tolerance ± 0.2 %, transverse sensitivity 0.9 ± 0.2 %
• Two versions: 2/4 bridge with two active gauges, or full bridge, the latter only with cable and connector
• Cannot be overloaded – an offset appears instead of damage
• Supply 5 V DC, 8 V DC at most, current draw below 15 mA

Mounting and use

• Clamped around the bar with two screws at 3 N·m – no adhesive, no drilling
• Works on any round bar, magnetic or not
• No chemical cleaning, no grinding – a solvent is enough; loose material such as rust or flaking paint has to go first
• 34 bar diameters from 50 to 400 mm, set in the order key
• Operating and storage temperature 0 … +55 °C
• Protection IP66 with connection C, IP40 with connection D
• Anodised aluminium housing, stainless steel cover
• Cable lengths 0.5 m, 3 m, 5 m and 10 m – connection C only
• Made for cyclical measurement, such as clamping force on presses

What you need with it

The ring is passive and needs an external amplifier. After mounting, the zero offset of the pressed-on gauges is high – an amplifier that resets it at the push of a button or by a signal therefore belongs to the measuring chain.

The ring is made to the bar diameter ordered. Beside the product code, its nameplate carries a type key of diameter, bridge, connection and cable length.