Probes outside of a holding tank

Thx for the link referrals- contacted Touchsensor's Jay Orellana 630 336-8811 (jayo@touchsensor.com)... an most excellent C Serv Rep! Offered to send, no charge, adhesive pads to resecure. He explained that air and conductive materials most impair performance of sensors and securing between tank and sensor with a correct material/adhesive is not a problem and actually advisable. The most perminate he suggested: 3M's marine 5200 careful to squeeze out air bubbles. Also interesting, he explained each sensor puts out an electric field when it detects a conductive mass disrupting the field and triggering indicating lights cumulatively. So floating "stuff" that can end up sticking on the wall of a tank even toward the top can trigger your first light regardless sensor location. As the sensor field detects mass, it lights up the next higher light indicator. This explains why so many get false readings even after the tank has been drained.