Information is entered and validated by the operator of a dialysis machine by converting the entered information into a first form using a first conversion relationship such as ASCII. The information in the first form is next converted into a second form using a second conversion relationship, such as floating point numeric. Thereafter the information in the second form is converted back to the first form using the first conversion relationship. The information in the first form which resulted from the third conversion is displayed for acceptance for rejection by the operator. The multiple sequential conversions indicate the proper functionality of a safety system of the dialysis machine. Displaying the information resulting from sequential multiple conversions assures an opportunity for the operator to evaluate the entries for accuracy. Re-display of the previously entered information repeatedly presents the operator with an opportunity to recognize human-induced errors.