PDF, manuals for the related DIG 400A Series or OptoSigma MD-400 provide general wiring and interface guidance.
If you cannot find a free copy, some sellers of used Digicon MD-400A units offer scanned manuals for a small fee ($1–$5). Read reviews before purchasing. Digicon Md-400a Manual Pdf
The Digicon MD-400A is a high-performance digital multimeter that offers a variety of functions, including DC and AC voltage measurements, DC and AC current measurements, resistance measurements, and more. Its accuracy, reliability, and user-friendly interface make it a preferred choice for professionals and hobbyists alike. PDF, manuals for the related DIG 400A Series