Optional alarm boards with high and low relays for each channel. Built-in thermal printer with external trigger control. Data cache with buffer. Some are smaller and more portable, using built-in memory to store data for later review. These usually include an RS-232 serial port for data download and a digital display.
Some models are battery-operated for easy portability in field applications.
20 Questions in Recorder Selection Given the wide variety of instruments for recording or logging acquired data, the prospective user needs to review the key factors involved in making a suitable selection. These are often called channels, points, or records. These may include absolute value, logarithm, exponential, maximum, minimum, time average, group average, summation, standard deviation, and integration functions. Z-fold has become the primary choice for process applications because of the ease with which an operator can review past traces without disrupting active recording. Continuous writing instruments provide the annotation by a separate printhead.