# What is the range of TDR on the 80E04?

### 問題：

What is the range of TDR on the 80E04?

### 答案：

This is a common question asked by people looking to purchase a TDR. This is a very important question that cannot be answered simply. Another important consideration is how close together the TDR can resolve features. This section discusses TDR range and the factors affecting it.

There are a number of factors that can affect the distance over which a TDR can locate features. The most important parameters that are TDR-related are step amplitude, step risetime, and step width.

Step amplitude is the amount of voltage produced by the TDR step. It is fixed for the 80E04 at 250 mV. In general, the higher the amplitude, the farther the TDR can see. Generally, this type of step is optimized for short range TDR.

Overall step width also affects range. It follows the setting of the Internal Clock Rate (25 kHz - 200 kHz). Step width is measured in time, but can also be thought of as distance when using a TDR. The longer the step width, the greater the range of the TDR. At 200 kHz, the step "on" time is 2.5 us - enough to see in air (one way transit) 375 meters (about 1,250 feet). To see events at greater distances, set the Internal Clock of the TDR to a lower frequency.