The new MetaScope 4
With its hardware upgraded, our new MetaScope 4 represents a smooth new step within our string of MetaScope items. Its black housing now features a larger RPi colour display with a capacitive touch function. Its control elements have been adapted to the new 800 x 480 pixel display format, which results in a much easier handling, similar to a smartphone. The connection for the magnetic stirrer has not been changed so that existing stirrers can also be operated with the new device, too. The operating concept and the Leoni measuring algorithm remain unaltered.
At higher frequencies electrical conductors experience a current displacement towards the surface called skin effect. In general a thick silver coating is used in high frequency applications. It is important to have a uniform plating thickness without any variations which can alter the conductor cross section and impact negatively on the conductor resistance.
Many conductive materials form an oxide layer when exposed to a normal atmosphere. This can cause problems when the material is further processed especially when it is exposed to high temperatures, e.g. when running conductors through an extrusion line.
Most standards and specifications require a minimum plating thickness. These are acceptance criteria for customers and it may be necessary to demonstrate exact results.
The coulometric principle
The coulometric transfer process according to DIN EN ISO 2177
DIN EN ISO 2177 describes the exact process and required materials for the coulometric (electrochemical) measuring of various metal combinations, e.g. tin plated, nickel plated or silver plated copper. Coulometry is a method used to calculate the exact amount of plating material present by removing it using an electric current. It can be regarded as the reversal of the electroplating process.
A probe is immersed into a relevant electrolyte and connected to a measuring device using a test lead. As soon as the power is switched on the plating material begins to separate itself from the conductor.
To conduct the measurement the amount of electrical charge (Q) is required. This can be determined using the following equation: Q = It (As)
where Q is the amount of electricity in coulombs, I is the current in amperes and t is the time in seconds. A constant current and exact time measurement are needed to obtain accurate results.
The graph depicts a typical example for silver plated copper. The abrupt end of the gradual increase signals the total removal of the silver plating. This point, caused by a change in resistance determines the measuring time (t).