X-Git-Url: https://sigrok.org/gitweb/?a=blobdiff_plain;f=src%2Fdmm%2Fut71x.c;h=9a7d2eab93b0776bd56e1a75fcaf9fea86887cb1;hb=45fcaf2ccad796b4bc4434d81b1d0e23f11a8eae;hp=01a8c22084400ed0490ce9520830e9237e601aeb;hpb=2ea1fdf12113311cbe1a4316e9e2efe4d8ac40f0;p=libsigrok.git

diff --git a/src/dmm/ut71x.c b/src/dmm/ut71x.c
index 01a8c220..9a7d2eab 100644
--- a/src/dmm/ut71x.c
+++ b/src/dmm/ut71x.c
@@ -44,7 +44,7 @@ static const int exponents[16][8] = {
 	{  0,  -4,  -3,  -2, -1,  0,  0,  0 }, /* DC V */
 	{  0,  -4,  -3,  -2, -1,  0,  0,  0 }, /* AC V */
 	{ -5,   0,   0,   0,  0,  0,  0,  0 }, /* DC mV */
-	{  0,  -1,   0,   1,  2,  3,  4,  0 }, /* Resistance */
+	{  0,  -2,  -1,   0,  1,  2,  3,  0 }, /* Resistance */
 	{  0, -12, -11, -10, -9, -8, -7, -6 }, /* Capacitance */
 	{ -1,   0,   0,   0,  0,  0,  0,  0 }, /* Temp (C) */
 	{ -8,  -7,   0,   0,  0,  0,  0,  0 }, /* uA */
@@ -81,9 +81,21 @@ static int parse_value(const uint8_t *buf, struct ut71x_info *info, float *resul
 		       buf[0], buf[1], buf[2], buf[3], buf[4]);
 		return SR_ERR;
 	}
+
 	for (i = 0, intval = 0; i < num_digits; i++)
 		intval = 10 * intval + (buf[i] - '0');
 
+	/*
+	 * For measurements that only have 4000 instead of 40000 counts
+ 	 * (resistance, continuity) we have to use an additional factor of 10.
+ 	 *
+ 	 * This seems to vary between DMMs. E.g. the Voltcraft VC920 and VC940
+ 	 * have 4000 counts for resistance, whereas the Tenma 72-9380A,
+ 	 * 72-7730 and 72-7732 have 40000 counts for resistance.
+ 	 */
+	if (num_digits == 4)
+		intval *= 10;
+
 	/* Apply sign. */
 	intval *= info->is_sign ? -1 : 1;
 
@@ -116,7 +128,7 @@ static int parse_range(const uint8_t *buf, float *floatval, int *exponent)
 
 	/* Apply respective exponent (mode-dependent) on the value. */
 	*floatval *= powf(10, *exponent);
-	sr_dbg("Applying exponent %d, new value is %f.", *exponent, *floatval);
+	sr_dbg("Applying exponent %d, new value is %g.", *exponent, *floatval);
 
 	return SR_OK;
 }