Environmental logging equipment is usually mounted in a small truck or a van, but more easily portable logging equipment has become quite popular and more practical with the advent of notebook computers. The equipment used for nonpetroleum logging is quite different from that used to log oil wells, and the cost of equipment and services tends to be much lower. Many modern loggers incorporate digital-recording equipment so that data from the probe may be displayed in digital and analog format. Most logging cable is double-wrapped with stainless steel wire to protect the insulated conductors inside and to serve as a strength member. The cable head often is the most troublesome component in a logging system. Electrical leakage in a cable head is common. Newer probes convert detected signals to a digital signal for transmission up the cable. The measuring sheave is precisely machined to provide accurate cable measurement and must be kept free of dry drilling mud or ice.