diff --git a/hardware/common/dmm/fs9922.c b/hardware/common/dmm/fs9922.c
index 9decc786..51d3c654 100644
--- a/hardware/common/dmm/fs9922.c
+++ b/hardware/common/dmm/fs9922.c
@@ -375,3 +375,17 @@ SR_PRIV int sr_fs9922_parse(const uint8_t *buf, float *floatval,
 
 	return SR_OK;
 }
+
+SR_PRIV void sr_fs9922_z1_diode(struct sr_datafeed_analog *analog, void *info)
+{
+	struct fs9922_info *info_local;
+
+	info_local = (struct fs9922_info *)info;
+
+	/* User-defined z1 flag means "diode mode". */
+	if (info_local->is_z1) {
+		analog->mq = SR_MQ_VOLTAGE;
+		analog->unit = SR_UNIT_VOLT;
+		analog->mqflags |= SR_MQFLAG_DIODE;
+	}
+}
diff --git a/hardware/serial-dmm/api.c b/hardware/serial-dmm/api.c
index b6987947..4e1e1e01 100644
--- a/hardware/serial-dmm/api.c
+++ b/hardware/serial-dmm/api.c
@@ -172,10 +172,15 @@ SR_PRIV struct dmm_info dmms[] = {
 		receive_data_VOLTCRAFT_VC820_SER,
 	},
 	{
+		/*
+		 * Note: The VC830 doesn't set the 'volt' and 'diode' bits of
+		 * the FS9922 protocol. Instead, it only sets the user-defined
+		 * bit "z1" to indicate "diode mode" and "voltage".
+		 */
 		"Voltcraft", "VC-830 (UT-D02 cable)", "2400/8n1/rts=0/dtr=1",
 		2400, FS9922_PACKET_SIZE, NULL,
 		sr_fs9922_packet_valid, sr_fs9922_parse,
-		NULL,
+		&sr_fs9922_z1_diode,
 		&voltcraft_vc830_ser_driver_info,
 		receive_data_VOLTCRAFT_VC830_SER,
 	},
diff --git a/hardware/uni-t-dmm/api.c b/hardware/uni-t-dmm/api.c
index e766fd85..b23fc02c 100644
--- a/hardware/uni-t-dmm/api.c
+++ b/hardware/uni-t-dmm/api.c
@@ -99,10 +99,15 @@ SR_PRIV struct dmm_info udmms[] = {
 		&voltcraft_vc820_driver_info, receive_data_VOLTCRAFT_VC820,
 	},
 	{
+		/*
+		 * Note: The VC830 doesn't set the 'volt' and 'diode' bits of
+		 * the FS9922 protocol. Instead, it only sets the user-defined
+		 * bit "z1" to indicate "diode mode" and "voltage".
+		 */
 		"Voltcraft", "VC-830", 2400,
 		FS9922_PACKET_SIZE, NULL,
 		sr_fs9922_packet_valid, sr_fs9922_parse,
-		NULL,
+		&sr_fs9922_z1_diode,
 		&voltcraft_vc830_driver_info, receive_data_VOLTCRAFT_VC830,
 	},
 	{
diff --git a/libsigrok-internal.h b/libsigrok-internal.h
index 5fc0fbfa..423463a2 100644
--- a/libsigrok-internal.h
+++ b/libsigrok-internal.h
@@ -213,6 +213,7 @@ struct fs9922_info {
 SR_PRIV gboolean sr_fs9922_packet_valid(const uint8_t *buf);
 SR_PRIV int sr_fs9922_parse(const uint8_t *buf, float *floatval,
 			    struct sr_datafeed_analog *analog, void *info);
+SR_PRIV void sr_fs9922_z1_diode(struct sr_datafeed_analog *analog, void *info);
 
 /*--- hardware/common/dmm/fs9721.c ------------------------------------------*/