D. K. Instruments pvt. Ltd. An iso 9001:2000 certified company manufactures a wide range of level, flow and pressure instruments. As a part of that hydrostatic level probe with fixed rod, hlf 842 is designed for short measurements with a fixed 316s.S. Rigid rod. There is no pre-set limit for rigid rod lengths, but the longer the rod gets, the more difficult it is to transport and install. Sitron recommends lengths no greater than 8 feet [2.43 m]; for lengths greater than 8 feet [2.43 m] the hlc 842, having no pre-set limit on cable lengths, is the ideal solution. The hlf 842 has an Electronic module in the probe`s housing with a zero/span adjustment.