Duncan Instruments provides quality data logger equipment. Data loggers and data recorders acquire digital data from sensors and other signals. They are primarily used to store data (for subsequent download to a host PC), but may also include real-time features including monitors and alarms. Important specifications to consider when searching for data loggers and data recorders include differential analog input channels, digital I/O channels, sampling frequency, resolution, and accuracy. Differential channels use the difference between two signals as an input; common mode is filtered out. In some systems, differential inputs are combinations of two single-ended inputs; in this case, twice the number of differential channels would be available as single-ended inputs. Digital or discrete channels are used for low-level on-off signals used in applications such as communication, user interface, or control. Sampling frequency is the frequency of the analog signal sampling and conversion to a digital value. Resolution refers to the degree of fineness of the digital word representing the analog value. A ten-bit number contains 210, or 1024, increments. A 0-10V signal could therefore be resolved into approximately 0.01V increments. A 12-bit representation would be in 212 (4096) increments, or divisions of 0.0024V for the same signal. Each additional bit doubles the resolution, and one bit is required for the polarity (sign) of a number. Data loggers and data recorders accuracy depends on the signal conditioning linearity, hysteresis, temperature considerations, etc.