Accuracy, precision and resolution

Accuracy, Precision and Resolution

Would you be able to tell the difference between accuracy, precision and resolution?

Accuracy refers to how close a frequency or power measurement is true to reality, whereas precision states measurement repeatability within a certain error margin. Check here for more details.

In general terms, accuracy and precision are of the same magnitude in RF Explorer so we may only specify one of them.

Resolution is a function from the selected frequency span. The wider the span the lower the resolution.

RF Explorer specific Frequency Accuracy

RF Explorer Model	Frequency accuracy	Internal reference device
Signal Generator RFE6GEN	0.5ppm	Advanced TCXO
Signal Generator Combo	0.5ppm	Advanced TCXO
6G COMBO PLUS	0.5ppm > 240MHz	Advanced TCXO and 30MHz XTAL
4G Combo PLUS	0.5ppm > 240MHz	Advanced TCXO and 30MHz XTAL
WSUB1G PLUS	10ppm	30MHz XTAL
ISM Combo PLUS	10ppm	30MHz XTAL
6G Combo	0.5ppm in 6GHZ 10ppm below 3GHz	Advanced TCXO and 30MHz XTAL
WSUB1G	10ppm	30MHz XTAL
3G Combo	10ppm	30MHz XTAL
2.4G	10ppm	26MHz XTAL
ISM Combo	10ppm	26MHz and 30MHz XTAL

Internal reference device specifications:

RF Explorer 6G WB PLUS	Standard	RFELIC03	RFELIC03 + RFELIC05
Expansion Frequency Range	15MHZ-6100MHz	15MHZ-6100MHz	15MHZ-7500MHz
Expansion Frequency Span	up to 960MHz	up to 3000MHz
Mainboard Frequency Range	N/A
Mainboard Frequency Span	N/A

Crystal tolerance is not the only factor that has influence in the initial accuracy of the unit. PCB parasitic capacitance and manufacturing tolerance plays an important role at these high frequencies. Due to this, you may expect up to +-100ppm initial value tolerance when uncalibrated for a crystal based device.

However, aging and stability is maintained within +-10ppm, in this case the crystal is the dominating factor (the parasitic capacitance is a manufacturing error and is not influenced by age or temperature).

Regardless of accuracy, the most limiting factor is resolution. Understanding it will help to get the best value from your instrument.

There are 112 sweep steps in RF Explorer Spectrum Analyzer screen. Therefore, the maximum resolution you can get is FreqSpan/112.

In other words, for a frequency span of 10Mhz, you get a resolution of 10,000Khz/112=89.3Khz . With this span in the 433Mhz band, it is clear that 89.3Khz is a larger value than 4.3Khz and therefore the accuracy doesn't play as much as an important role as resolution.

If you now reduce the span to 200Khz, then resolution gets as fine as 200Khz/112=1.8Khz . In this case, the resolution is finer than accuracy and then accuracy is the main factor to consider.

Frequency Calibration demonstration video

We keep developing additional firmware features to offer additional calibration capabilities to reach sub-KHz accuracy and better amplitude accuracy in all bands.