Selig is now offering the NanoRanger NR-01 -- designed by AltoNovus -- an affordable, highly accurate 3.5-bit DC ammeter for precise measurement of very low currents. Automatic dynamic range (nine ranges across 8.5 years), the device measures current from 1nA to 800mA with a maximum resolution of 10pA. Each instrument is factory calibrated, eliminating the need to use high-cost precision components in the design, thus keeping the purchase price low. The current is measured by a 12-bit ADC, which is oversampled and automatically averaged to provide a 16-bit result. Every 170 samples were sampled. Readings are displayed every 300mS, built on 180 average samples, to remove line noise (50Hz and 60Hz). Another "fast sampling" mode can sample 150 times per second.
Backlit 11-bit 128 x 64 LCD provides rich information on the current reading; For example, mA, uA, nA, pA are all on the same line. Run average readings (current and elapsed time) enable users to measure the power consumption of events, such as radio transmissions. The coverage bar shows the coverage of the whole measurement process; It can be enclosed in parentheses, or it can be confined to a range. A signal-to-noise ratio display shows how much noise or alternating current is present in the current signal. Minimum and maximum ranges can be changed to limit automatic ranging or fixed in a range.
There are challenges when trying to measure the power consumption of low-power circuits in offline or standby mode. Typically, current consumption is in the nA or pA range, beyond the capabilities of most DMM, but the device can accurately measure these ranges. A 6.5 bit DMM with 1nA resolution has a minimum range of 2.000000mA and absolute accuracy may be only +/-500 na. The device has a selectable range of measurements for each decade. It features a fully isolated USB interface for device control and data export. Full isolation means that a USB connection does not adversely affect measurements.
The device is designed to reduce the load voltage below 50mV during low power current measurements. A large load voltage may affect the circuit under test, thus ruining the measurement. For this reason, it is desirable to keep the load voltage as low as possible.
