Foil strain gage for automated handling and packaging
View Patent ↗An improved strain gage and an improved manufacturing method are disclosed. The strain gage includes a semi-rigid substrate having a thickness of 3 to 30 mils, a resistive strain sensitive foil bonded to the semi-rigid substrate for providing a resistance varying with strain associated with a surface to which the strain gage is attached, a first and a second terminal operatively connected to the resistive strain sensitive foil, and an anti-static layer. The improved strain gage allows for reduced labor content in manufacturing by allowing use of modern automated electronic component manufacturing equipment.
1. A strain gage adapted for providing improved packaging and installation comprising:
a semi-rigid substrate having a thickness of 3 to 30 mils and a modulus of elasticity of at least 200,000 pounds per square inch to thereby provide sufficient substrate thickness such that the semi-rigid substrate provides for improved packaging and installation;
a resistive strain sensitive foil bonded directly to the semi-rigid substrate for providing a resistance varying with strain associated with a surface to which the strain gage is attached; and
a first and a second terminal operatively connected to the resistive strain sensitive foil.
2. The strain gage of claim 1 wherein the resistive strain sensitive foil provides a resistance of between about 50 and about 10,000 ohms.
3. The strain gage of claim 1 further comprising an anti-static layer overlaying a surface of the resistive strain sensitive foil.
4. The strain gage of claim 3 wherein the anti-static layer is adapted for soldering the strain gage to a metal part.
5. The strain gage of claim 1 further comprising an anti-static layer overlaying a surface of the semi-rigid substrate opposite the resistive strain sensitive foil.
6. The strain gage of claim 5 wherein the anti-static layer is metal.
7. The strain gage of claim 5 wherein the anti-static layer is adapted for soldering the strain gage to a metal part.
8. The strain gage of claim 1 wherein the semi-rigid substrate is glass reinforced epoxy.
9. The strain gage of claim 1 wherein the semi-rigid substrate is polyimide.
10. The strain gage of claim 1 wherein the semi-rigid substrate is phenolic.
11. The strain gage of claim 1 wherein the semi-rigid substrate is metal.
12. The strain gage of claim 1 wherein the first and second terminals are presoldered for facilitating lead attachment.
13. The strain gage of claim 1 wherein the strain sensitivity remains greater than 50 percent of the normal strain sensitivity of the resistive material despite the thickness and rigidity of the semi-rigid substrate.
14. The strain gage of claim 1 comprising resistive materials with normal strain sensitivities, k, between 2 and 150.
15. A strain gage, comprising:
a semi-rigid substrate having a thickness of 3 to 30 mils and a modulus of elasticity of at least 200,000 pounds per square inch;
a resistive strain sensitive foil bonded to the semi-rigid substrate for providing a resistance varying with strain associated with a surface to which the strain gage is attached;
a first and second terminal operatively connected to the resistive strain sensitive foil;
an anti-static layer overlaying a surface of the strain gage;
the semi-rigid substrate adapting the strain gage for packaging in tape and reel;
the anti-static layer adapting the strain gage for sorting with vibrating bowls.
16. The strain gage of claim 15 wherein the semi-rigid substrate having a modulus of elasticity of at least 200,000 pounds per square inch.