diff --git a/include/probe.h b/include/probe.h
index 96df621..34871f0 100644
--- a/include/probe.h
+++ b/include/probe.h
@@ -16,6 +16,9 @@ void probe_mode_switch(uint8_t mode);
 
 void probe_measure();
 
+void probe_set_thresh(uint8_t set);
+uint8_t probe_get_thresh();
+
 
 
 #endif /* _INC_PROBE_H */
\ No newline at end of file
diff --git a/include/userio.h b/include/userio.h
index 65b79cf..0e5000b 100644
--- a/include/userio.h
+++ b/include/userio.h
@@ -34,6 +34,9 @@ int16_t userio_get_btn();
 
 uint8_t userio_get_set1_limit();
 
+int16_t userio_get_btn_held();
+void userio_set_btn_override();
+
 
 
 #endif /* _INC_USERIO_H */
\ No newline at end of file
diff --git a/src/probe.c b/src/probe.c
index 639450e..d63b87f 100644
--- a/src/probe.c
+++ b/src/probe.c
@@ -3,6 +3,9 @@
  *
  * this file is responsible for figuring out the
  * continuity and diode tests from the raw analog data.
+ * 
+ * todo: confirm mathematically that continuity values
+ *       match the measured values
  *
  * file creation: 20231016 0255
  */
@@ -22,29 +25,52 @@
 
 
 // diode measurements at 3V3
-#define DIODE_OPEN			4000		// test unit measures ~4060
-#define DIODE_STANDARD		2330		// fairchild 5V2 zener, forward biased
+#define DIODE_OPEN			3860		// test unit measures ~4060 no D1, ~3960 with D1
 #define DIODE_SCHOTTKY		1960		// vishay 40V 1A SB140
+#define DIODE_STANDARD		2330		// fairchild 5V2 zener, forward biased
 #define DIODE_LED_BLUE		3190
 #define DIODE_LED_GRN		3040		// very dim
 #define DIODE_LED_RED		3020
 #define DIODE_SHORT			1900		// test unit measures ~1820
 
-#define SHORT_THRESHOLD		2
+
+#define CONT_SHORTED		858			// worst case measured value of short
+#define CONT_47OHM			869			// measured value of 47ohm 1% resistor at room temp
+#define CONT_100OHM			886			// measured value of 100ohm 1% resistor at room temp
+#define CONT_EXTRA_COUNTS	8			// extra raw counts as a fudge factor, post-scaling
+#define CONT_LATCH_THRESH	15			// extra raw counts for latching indicator, post-scaling
+
+#define CONT_LATCH_TIMEOUT	4			// probe measurement passes to hold latched indicator
 
 
 
 static uint16_t vref;
 
+static uint16_t cont_thresh_set = 0;
+static const uint16_t cont_thresh[] = {
+	CONT_100OHM, CONT_47OHM
+};
+
 static uint8_t latch = 0;
 static uint8_t buzzer = 0;
 
 
 
+void probe_set_thresh(uint8_t set)
+{
+	cont_thresh_set = set;
+}
+
+uint8_t probe_get_thresh()
+{
+	return cont_thresh_set;
+}
+
 static inline void probe_measure_cont()
 {
 	uint16_t probe, v_ext;
-	uint32_t x;
+	uint32_t x, c;
+	uint8_t g, b;
 
 	probe = adc_avg[ADC_PROBE];
 	v_ext = adc_avg[ADC_VREF_EXT];
@@ -54,29 +80,45 @@ static inline void probe_measure_cont()
 		buzzer ^= 1;
 	}
 
+	// if the button has been held, change the threshold
+	if (userio_get_btn_held() == 60) {
+		userio_set_btn_override();
+		cont_thresh_set ^= 1;
+	}
+
 	// this LED will not set anything,
 	// but zero it out anyway
 	led_setrgb(1, 0, 0, 0);
 	
 	if (vref) {
-		x  = probe << 12;			// maximum possible level
-		x /= vref;					// normalize to 4096max
+		// probe level
+		x  = probe << 12;					// maximum possible level
+		x /= vref;							// normalize to 4096max
 		if (x > 4095) x = 4095;
 
-		if (x < 2405) {				// roughly 100ohm or lower
-			latch = 4;				// latch any continuity for a while
+		// threshold level
+		c  = cont_thresh[cont_thresh_set] << 12;
+		c /= vref;
+
+		// are we measuring a lower value?
+		if (x < (c + CONT_EXTRA_COUNTS)) {	// roughly 100ohm or lower
+			latch = CONT_LATCH_TIMEOUT;		// latch any continuity for a while
 		}
 
-		if (latch) {
-			// indicate continuity
-			if (x >= 2420) latch--;	// hysteresis
+		b = buzzer ? 100 : 0;
 
-			led_setrgb(0, 0, 250, ((buzzer) ? 100 : 0));
+		if (latch) {
+			// hysteresis
+			if (x >= c + CONT_LATCH_THRESH) latch--;
+
+			// indicate continuity
+			led_setrgb(0, 0, 250, b);
 			led_buzz(0);
 			if (buzzer) led_buzz(1);
 		} else {
 			// idle
-			led_setrgb(0, 120, 0, ((buzzer) ?   8 : 0));
+			g = cont_thresh_set ?  40 :  0;
+			led_setrgb(0, 120, g, b);
 			led_buzz(0);
 		}
 	}
@@ -97,23 +139,23 @@ static inline void probe_measure_diode()
 	if (p < DIODE_SHORT) {
 		// show off on short
 		led_setrgb(1, 0, 0, 0);
-	}
-
+	} else
 	if (p >= DIODE_OPEN) {
 		// show red on open
 		led_setrgb(1, 120, 0, 0);
-	}
-
+	} else
 	if (p >= 1940 && p < 2650) {
 		// show green on regular or schottky diodes
 		led_setrgb(1, 0, 200, 0);
-	}
-	if (p >= 2650 && p < 3800) {
+	} else 
+	if (p >= 2650 && p < 3700) {
 		// show blue on LEDs
 		led_setrgb(1, 0, 0, 500);
+	} else
+	if (p >= 3701) {
+		// show red+blue if between open and LED
+		led_setrgb(1, 120, 0, 120);
 	}
-
-	// if we haven't set a value, flash red to indicate error state
 }
 
 void probe_measure()
diff --git a/src/userio.c b/src/userio.c
index d2a020f..00c624b 100644
--- a/src/userio.c
+++ b/src/userio.c
@@ -41,6 +41,11 @@
 #define MODE_ANALOG_MIN     20
 
 
+#define BTN_OPEN			0
+#define BTN_PUSHED			1
+#define BTN_OVERRIDE		2
+
+
 #ifdef TESTO_REV1
 #define SET1_MAX			2199	// 3V net feeding into 1V24 via body diode above this
 #else
@@ -76,9 +81,12 @@ void userio_parse()
 		m = adc_avg[ADC_SET_MODE];
 		if (m < MODE_ANALOG_MIN) {
 			// button is pushed
-			btn = 1;
+			if (btn == BTN_OPEN) btn = 1;
 			if (btn_held != 0xffff) btn_held++;
-		} else if (btn == 1) {
+		} else if (btn) {
+			// release held count if overridden
+			if (btn == BTN_OVERRIDE) btn_held = 0;
+
 			// button is released
 			btn = 0;
 		}
@@ -165,8 +173,8 @@ int16_t userio_get_btn()
 {
 	int16_t ret;
 
-	if (btn) return -1;
-	if (!btn) {
+	if (btn == BTN_PUSHED) return -1;
+	if (btn == BTN_OPEN) {
 		if (btn_held) {
 			ret = btn_held;
 			btn_held = 0;
@@ -177,6 +185,24 @@ int16_t userio_get_btn()
 	return 0;
 }
 
+/*
+ * returns the button state.
+ *  0 = not held
+ * >0 = held for X ticks
+ */
+int16_t userio_get_btn_held()
+{
+	return btn_held;
+}
+
+/*
+ * overrides and disables the next button release event.
+ */
+void userio_set_btn_override()
+{
+	btn = BTN_OVERRIDE;
+}
+
 /*
  * returns true if the right knob is beyond maximum range.
  * always returns false on REV2 or later boards.