Does the 200CR (or other model) come in an explosion proof or intrinsically safe version to meet a Class I, Division 1 location requirement?
Thornton instruments are used primarily in safe locations for water treatment. However, occasional users need installation in hazardous areas. A user has installed the 200CR in a windowed explosion-proof box with explosion-proof conduit running to a sensor with NPT threaded top.
Others have used intrinsic safety barriers with the 200CR. Typically two are required, one for the AC conductivity signal and one for the DC temperature signal. On-site temperature calibration is required at startup to compensate for barrier resistance. Because conductivity sensors consist of simple electrode contacts and a 1000 ohm RTD, they qualify as simple apparatus and do not require agency approval.
Because locations seem to have their own preference for barrier brand, we have not standardized on a recommendation of barrier. 200pH instrumentscannot be used with intrinsic safety barriers because of incompatible grounding.
Class I, Division 2 locations do not require explosion-proofing or intrinsic safety barriers although they may be used. Division 2 requirements can be met by apparatus that is non-incendive: apparatus that does not have any high temperature components or open contacts that would arc in normal operation that could ignite a flammable gas. Thornton conductivity and pH sensors operate at very low power and can be considered non-incendive although they have not been evaluated by an independent agency for this.