How to Calculate True Position

How to Calculate True Position
••• golubovy/iStock/GettyImages

Electrical engineers design and build electrical devices such as printed circuit boards and associated mechanical components. The first step in this process is producing a computer-aided design drawing that outlines the locations of wires, bonding pads and drilled holes. True position is the deviation of a feature on the product from its theoretical position on a drawing, and this position can be calculated using simple formulas.

Carrying Out Measurements

The first step in determining the true position is to carry out measurements on the product and compare these measurements to the original drawings. This process makes use of standard engineering tools, including micrometers, height gauges and calipers.

An Example in Carrying Out Measurements

Suppose a product consists of a single plate with a single drilled hole. In the following measurements, the plate origin (0,0) in standard Cartesian (x,y) coordinates is assumed to be on the bottom left-hand side of the plate. A caliper can be used to determine the position of the closest and farthest points of the hole on the x and y axes. For the sake of this example, assume that the closest and farthest measurements on the x axis are 15 mm and 20 mm, and the closest and farthest measurements on the y axis are 35 mm and 40 mm.

An Example in Calculating Hole Centerline

The centerline of a hole is calculated using the closest and farthest measurements of the hole on each of the coordinate axes. To calculate the centerlines on each axis use the following formula: center line = closest position + (farthest position – closest position)/2. Following the example in section 2, the center lines of the single hole on each axis are as follows: center line on x axis = 15 + (20 – 15 )/2 = 17.5 mm, and center line on y axis = 35 + (40 – 35)/2 = 37.5 mm.

An Example in Calculating True Position

True position is the deviation between the theoretical position on a drawing and the actual position, measured as the centerline, on the final product. True position can be calculated using the following formula: true position = 2 x (dx^2 + dy^2)^1/2. In this equation, dx is the deviation between the measured x coordinate and the theoretical x coordinate, and dy is the deviation between the measured y coordinate and the theoretical y coordinate. Following the example, if the theoretical coordinates of the drilled hole are (18 mm, 38 mm) then the true position is: true position = 2 x ((18 – 17.5)^2 + (38 – 37.5)^2)^1/2 = (0.25 + 0.25)^1/2 = 0.71 mm.

Related Articles

How to Find the Vertices of an Ellipse
How to Calculate Correlation Coefficients With an Equation
How to Calculate Calibration Curves
How to Calculate the Diameter of a Rectangle
How to Find a Z Score
How to Find the Radius of a Circle With the Midpoint
What Is MQ in the Metric System?
How to Calculate Binomial Probability
How to Calculate the Standard Error of a Slope
How to Calculate Axial Force
How to Read Dimensions
How to Find the Equation of a Scatter Plot
The Dimensions of a NEMA 56C
How to Use a Bushnell Reflector Telescope
How to Find the Area of a Parallelogram With Vertices
How to: Simple Homemade Sextant
How to Calculate the Cubic Feet of a Hole
How to Factor Trinomials on a TI-84
How to Calculate SSE
How to Calculate Catenary

Dont Go!

We Have More Great Sciencing Articles!