High-Temperature and High-Pressure, Pressure-Balanced Ag/AgCl Reference Electrodes are divided into three types (A, B, and C) and two designs (External Reference Electrode or Internal Reference Electrode).
Types A and B have a compression fitting and an insertion tube. Type A has an NPT fitting with a metal seal that will be locked to the insertion tube after first use (insertion depth one-time adjustable only). Type B has an NPT fitting with a soft seal that can be repositioned on the insertion tube after each use (insertion depth fully adjustable). The NPT fittings for Types A and B are sold separately.
Type C has a threaded fitting. If the NPT size is 1/4" or larger, a thin-walled protection tube may be provided . Type C is ultra compact and may be used in autoclaves that have smaller access ports (1/8"). The insertion depth for Type C is fixed at factory (non adjustable). Type C is available for internal design only.
External design: Reference material (Ag/AgCl) is away from heated location and maintained near ambient temperature so that the probe is more stable when used at T>200°C.
Internal design: Reference material (Ag/AgCl) is in heated location so that the probe has a better defined thermodynamic potential. Not recommended for long-term use at T>200°C.