Product Description

803-T Invar Kit

English unit kit with 45° optical targets

The 803-T is designed as a calibration reference or scaling kit for theodolite systems and similar three-dimensional measuring equipment.   It can also be used in the construction of monuments or artifacts for “leapfrogging”, providing stable transfer points with optical targets.

Invar tubing is great for metrology because it has such a very low coefficient of thermal expansion, which effectively eliminates changes in length due to handling or environmental changes.

Invar Tubes 12587 Series
Tube Length Tolerance ±0.0001″
Total Stack-up Error ±0.0005″
The Invar tubing in the 803-T is manufactured to its stated length within ±0.0001″. In addition, the tubing components are hand-picked for each kit so that the total Invar stackup error does not exceed 0.0005″. This means that you can connect all of the tubes found in a given kit together end-to-end, and the stack will maintain the total length within the stackup error. (The table above right summarizes this information.) We often recommend the 803-T when people ask for a calibration or scaling-quality type system to be used with a theodolite measurement system.

Individual components may be assembled to produce lengths from 8″ to 113″, in 5″ increments. The table below specifies all included components. 

803-T Invar Kit Components

Legend Part Number Description Qty
A 12587-20IN 20″ Invar Tube 4
12587-10IN 10″ Invar Tube 2
12587-5IN 5″ Invar Tube 2
B 15960-1-.25 Target Holder 2
C 18-0001 Optical Target 2
D 12406-G1 Stainless Steel Invar System Connectors 8
no photo 12421-G1 Plastic Case 1
no photo NIST Traceable Certification for Kit 1


Approx. weight:
Kit and case, 17 lbs.
Shipping, 22 lbs.
Thermal expansion coefficient:
0.70×10−6 in./in./°F for temperature range of 0°F to 200°F
Invar tubing:
1″ diameter Invar with stainless steel end caps, having 3/8″-24 internal threads on each end
Finish: Oil and stain resistant PVC jacket (red)
Case: Plastic case with foam insert