diff --git a/pc/calibrate.c b/pc/calibrate.c
index b5aeddd..170ee36 100644
--- a/pc/calibrate.c
+++ b/pc/calibrate.c
@@ -81,7 +81,7 @@ int main(int argc, char *argv[])
 
 void calibrate(int zoom, int gpib)
 {
-	float idesired, iactual;
+	double idesired, iactual;
 	int i;
 	int zero;
 	int r = 0;
@@ -111,10 +111,10 @@ void calibrate(int zoom, int gpib)
 		info("Zeroing\n");
 		if (zoom_zero_start(zoom) < 0) goto fail;
 		
-		info("Setting current: %f\n", idesired);
+		info("Setting current: %.8f\n", idesired);
 		keithley_current(gpib, idesired);
 		iactual = keithley_read(gpib);
-		info("Actual current: %f\n", iactual);
+		info("Actual current: %.8f\n", iactual);
 
 		info("Stop zeroing\n");
 		if ((zero = zoom_zero_stop(zoom)) < 0) goto fail;
@@ -125,7 +125,7 @@ void calibrate(int zoom, int gpib)
 
 		info("Results:\n");
 		for (i = 0; i < ZOOM_SWEEP_COUNT; i++) {
-			printf("%8f %d %d\n", iactual, dac[i], adc[i]);
+			printf("%.8f %d %d\n", iactual, dac[i], adc[i]);
 		}
 	}
 
diff --git a/pc/gpib.c b/pc/gpib.c
index 340d853..4ae3f2b 100644
--- a/pc/gpib.c
+++ b/pc/gpib.c
@@ -33,7 +33,7 @@ int gpib_addr(int fd, int addr)
 
 int keithley_init(int fd)
 {
-	float i;
+	double i;
 	gput(":syst:beep:stat 1");
 	gput(":sour:func:mode curr");
 	gput(":sour:del 0");
@@ -47,7 +47,7 @@ int keithley_init(int fd)
 	return 0;
 }
 
-int keithley_current(int fd, float amps)
+int keithley_current(int fd, double amps)
 {
 	char s[128];
 	sprintf(s, ":sour:curr %0.3f", amps);
@@ -55,15 +55,16 @@ int keithley_current(int fd, float amps)
 	return 0;
 }
 
-float keithley_read(int fd)
+double keithley_read(int fd)
 {
 	char s[128];
-	float i, dummy;
+	double i, dummy;
 	gputv("read?", NAN);
 	gputv("++read", NAN);
 	if (fdgets(s, 128, fd, 2000) == NULL)
 		return NAN;
-	if (sscanf(s, "%f,%f,", &dummy, &i) != 2)
+	printf("%s\n", s);
+	if (sscanf(s, "%lf,%lf,", &dummy, &i) != 2)
 		return NAN;
 	return i;
 }
diff --git a/pc/gpib.h b/pc/gpib.h
index 4155f9c..e387c9b 100644
--- a/pc/gpib.h
+++ b/pc/gpib.h
@@ -5,8 +5,8 @@ int gpib_init(int fd);
 int gpib_addr(int fd, int addr);
 
 int keithley_init(int fd);
-int keithley_current(int fd, float amps);
-float keithley_read(int fd);
+int keithley_current(int fd, double amps);
+double keithley_read(int fd);
 int keithley_off(int fd);
 
 #endif