Method for the error-protected acquisition of a measured value in a control unit, wherein the measured value is firstly acquired with a first acquisition means and secondly with a second acquisition means and thereby a first measured value and a second measured value are made available, wherein in a comparison step in a safety program running in the control unit, the first and the second measured value (AI1, AI2) are compared with one another for a deviation from one another and on reaching or exceeding a pre-determined maximum deviation (minV, maxV), an error is identified, characterised in that the first acquisition means is parameterised for a first measurement range that is to be set with fixed parameterisation from 0 to 20 mA, that the second acquisition means is parameterised for a second measurement range that is to be set with alternating parameterisation from 0 to 20 mA and from 4 to 20 mA, that the second measurement range for the second acquisition means is alternatingly reparameterised, wherein a start signal functions as a trigger and each time the start signal is applied, the respectively valid parameter set in the second acquisition means is reparameterised to the other parameter set on an alternating basis, that a plausibility check between the first measured value and the second measured value is carried out in the safety program, such that analogue-digital converters are utilised in the acquisition means (11, 12) and the analogue-digital converter in the first acquisition means provides a first integer value for the first measured value and the analogue-digital converter in the second acquisition means provides a second integer value for the second measured value, to which the plausibility check is applied, wherein the safety program contains a first converter curve, which is configured for an analogue-digital converter with a parameterisation from 4 to 20 mA, and a second converter curve, which is configured for an analogue-digital converter with a parameterisation from 0 to 20 mA, and that if a plausibility check result is negative, an error is also identified. wherein in a comparison step in a safety program running in the control unit, the first and the second measured value (AI1, AI2) are compared with one another for a deviation from one another and on reaching or exceeding a pre-determined maximum deviation (minV, maxV), an error is identified, characterised in that the first acquisition means is parameterised for a first measurement range that is to be set with fixed parameterisation from 0 to 20 mA, that the second acquisition means is parameterised for a second measurement range that is to be set with alternating parameterisation from 0 to 20 mA and from 4 to 20 mA, that the second measurement range for the second acquisition means is alternatingly reparameterised, wherein a start signal functions as a trigger and each time the start signal is applied, the respectively valid parameter set in the second acquisition means is reparameterised to the other parameter set on an alternating basis, that a plausibility check between the first measured value and the second measured value is carried out in the safety program, such that analogue-digital converters are utilised in the acquisition means (11, 12) and the analogue-digital converter in the first acquisition means provides a first integer value for the first measured value and the analogue-digital converter in the second acquisition means provides a second integer value for the second measured value, to which the plausibility check is applied, wherein the safety program contains a first converter curve, which is configured for an analogue-digital converter with a parameterisation from 4 to 20 mA, and a second converter curve, which is configured for an analogue-digital converter with a parameterisation from 0 to 20 mA, and that if a plausibility check result is negative, an error is also identified.