added some comments about how internal voltage reference appears when

using +-50V or +-20V input ranges

diff --git a/comedi_calibrate/ni.c b/comedi_calibrate/ni.c
index 695ea0a05904ad8286b70f390290d18434518443..0f4005738f3246b9223dbb5dec1ab1516b32e1d6 100644 (file)
--- a/comedi_calibrate/ni.c
+++ b/comedi_calibrate/ni.c
@@ -313,12 +313,13 @@ void ni_setup_observables( calibration_setup_t *setup )
        }
 }
 
+/* XXX for +-50V and +-20V ranges, the reference source goes 0V
+ * to 50V instead of 0V to 5V */
 static unsigned int cal_gain_register_bits_611x( double *voltage )
 {
        unsigned int bits;
 
        bits = 200.0 * ( *voltage / 5.0 );
-       if( bits < 1 ) bits = 1;
        if( bits > 200 ) bits = 200;
 
        *voltage = 5.0 * ( bits / 200.0 );