| 摘要 |
A first measuring value signal is determined by a first measuring tube (1), whose ratio (V) of length (L) to the inside dia (D) is larger than a specified number (1.3), with which the faults can be neglected. A second signal is determined by a second tube (1), the ratio of (V) of length (L) to the inner dia. (D) of which, is smaller than the specified number (1.3), depending on the electrical conductivity of the connecting tubes, under the same conditions as the first signal. A first quotient (Ki) is formed from the first and second value signals. A constant voltage (generator G) is applied at a first pair (3a, 3b) of each second measuring tube (1). Measurement voltages (U1,U2) are tapped from a second pair (4a,4b) and a third pair (5a,5b) of electrodes of each second measuring tube, and in certain cases amplified, amplifier (6). Second quotients (U1/U2) are formed from these voltages (U1,U2). These second quotients are allocated to the first quotients (Ki) in a storage (8). The second quotient (U1,U2)x) is determined in a 3rd measuring tube (10, installed in a use place. The associated 1st quotient (K) is abstracted from the storage (8) across a second quotient (U1/U2)i) corresp. tot he determined second quotient (U1/U2)x). The measuring value signals of the 3rd measuring tube are multiplied with the first quotient (K) as a correction value.
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