| abstract |
A microprocessor-controlled pH and ion concentration meter is disclosed with improved calibration and testing procedures. For calibration (standardization), the meter stores number pairs (pX a , E a ), (pX b , E b ) where the pX values may be pH values (e.g., 4.00 and 7.00) and the E values are expressed in mV/deg K. When multiple standard values are stored, remeasuring one (e.g., replacing E a1 by E a2 ) can be used to update the others (e.g., E b1 to E b2 ) without remeasurement by applying the formula: n n E.sub.b2 =E.sub.b1 +(E.sub.a2 -E.sub.a1). n n Additionally, the meter can be tested for excessive internal bias current by measuring the potential (V1) when the meter is connected to a circuit of low impedance and the potential (V2) when the meter is connected to a circuit of the same voltage source but of known high impedance and having the meter compare (V2-V1) to a preset limit value. |