Thankyou for your post with regard to the ADC-20. In this instance the ADC-20 would not be suitable for measuring frequency's up to 1 Mhz. The internal ADC does not accommodate the conversion time you require. In essence this logger is not suitable for high speed signals. The conversion times and voltage input levels are shown below:-
Conversion time (per channel) 660 ms, 340 ms, 180 ms, 100 ms, 60 ms
Input voltage ranges 2 ranges ±1250 mV and ±2500 mV
Channel to common ±1.9 V (±39 mV to ±1250 mV ranges)
Channel to common ±3.0 V (±2500 mV range)
Common to earth ground ±30 V
The ADC-20 and ADC-24 High-Resolution Data Loggers offer the ultimate in precise and accurate readings. Features such as true differential inputs, galvanic isolation and software-selectable sample rates all contribute to a superior noise-free resolution. The ADC-20 is equipped with a 20-bit A/D converter, and can maintain a gain error of 0.2%. The four true differential inputs may be configured as eight single-ended inputs or any combination in between, such as two differential and four single-ended. The ADC-24 is equipped with a 24-bit A/D converter, and can maintain a gain error of 0.1%. The eight true differential inputs may be configured as 16 single-ended inputs or any combination in between. Power and connection to a PC or laptop is through a USB 1.1 or USB 2.0 port.
If you let me know a little about your signal parameters I will endeavour to assist you further.