Many Tektronix oscilloscopes have a insulated ring around the BNC connector called the readout ring. This "tells" the scope via the pin on the probe the multiple (10x or 100x) value of the probe and changes the displayed voltage to the correct value on the scope.



Many Tek probes have this pin. Most non-Tek probes don't. Most of the basic Tek scopes (like the Tek 2225) also don't have a readout ring, but have two labels on the switch to indicate the V/DIV settings. Some also have a pull out knob to multiply the value 10x(as on the 2225 below.



Scopes with a readout ring and a compatible probe are a great convenience. When you change or switch the probe, the scope follows along automatically displaying the proper values. (My modern digital scope requires a menu change on the scope when changing the probe switch settings) Scopes with the readout ring, typical also have no method to manual "tell" the scope that your probe is at 10x. They don't have a menu.


If you have a 10x probe, without a readout pin, the scope will stay in 1x mode and your vertical scale will be off (by 10x). You have to do the math in your head. It's not too big a deal to mentally jump from say 0.5 to 5, but you do have to pay attention.


Most of these higher end scopes also have cursors or automatic value displays and they will be off too. It's annoying to have to pay attention to your values, when you are troubleshooting an issue. The issue: These great scopes are dependent on the readout pin, and don't have a manual (Menu) method to switch the scope to match the probe. The TekRing strives to solve this issue. Click on the Solution to see one the TekRing solution.