I don’t know if you have noticed that basically all instruments involved in frequency and power accuracy measurement require a period of startup warm-up time. Why?

It is usually based on two considerations:

1. The frequency source needs a certain time to warm up to reach a stable frequency output;

2. The analog device needs a certain time to warm up to achieve an expected stable performance;

We describe the following two points separately: In order to achieve accurate frequency measurement of the instrument, it is usually necessary to use a high-precision frequency source: TCXO or OCXO; among them, the frequency stability of TCXO is 10-6~10-7, and the frequency stability of OCXO It can reach 10-8~10-9. From the magnitude point of view, it can be seen that the stability of OCXO is originally higher than that of TCXO. Of course, the price of OCXO is also much higher than that of TCXO; so generally only high-end instruments will be used To OCXO; here WT200/WT208 use frequency sources are OCXO;

The OCXO needs a warm-up time to achieve a stable frequency output; that is, the main reason why high-precision frequency measuring instruments require a certain warm-up time;

Another reason is that usually analog devices: indicators are slightly different at different temperatures; the following figure shows the gain of a typical amplifier at different temperatures. Although the change is small, it is still for high-precision instruments. It needs to be taken into account; for this point, WT200/WT208 adopts temperature compensation, which means that within the instrument specification temperature range, the instrument can achieve high-precision measurement through a precise temperature compensation strategy; but the temperature compensation strategy needs to be based on the temperature of the board The best effect can be produced under the condition of balance; therefore, the preheating can effectively ensure the measurement accuracy of the instrument;