Features: · Limit sensing of almost any fluid or powder
· 2-Tier level sensor - Hi / Low limits with one probe
· Only one external part required - a 5¢ capacitor
· Uses internal probes or external electrodes
· Active high or active low outputs
· Slosh filter averages response of moving fluids
· LED drive capable on both outputs
· 2.5 to 5V 20µA single supply operation
· HeartBeat™ health indicator on both outputsApplication· Process controls
· Vending machines
· Automotive fluids
· Consumer appliances
· Medical fluid sensing
· Soil moisture sensingPinout
SpecificationsOperating temp . . . . . . . . . . . . . . . . . . . . . . .. as designated by suffix
Storage temp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55 to +125
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . -0.5 to +6.5V
Max continuous pin current, any control or drive pin .. . . . . . . ±20mA
Short circuit duration to ground, any pin . . . . . . . . . . . . . . . . . infinite
Short circuit duration to VCC, any pin . . . . . . . . .. . . . . . . . .. . . infinite
Voltage forced onto any pin . . . . . . . . . . ... . -0.6V to (Vcc + 0.6) VoltsDescriptionThe QT114 QuickLevel" charge-transfer ("QT") sensor IC is specifically designed to detect point level in fl ids
and powders. It will project a sense field through almost any dielectric, like glass, plastic, or ceramic, to sense level on the inside of a vessel, from its exterior. It has the unique capability of independently sensing two trip points when used with structured electrodes having two tiers.
The QT114 does not have sensing timeouts, drift compensation, or other functions which would interfere with level sensing. Its threshold levels are fixed, and the amount of signal required to exceed a threshold is dependent on circuit gain and electrode size and loading, all of which are under the control of the designer.
The QT114 requires only a single inexpensive capacitor in order to function. One or two LEDs can also be added to provide a visual sensing indication.
Power consumption is under 20mA in most applications, allowing operation from Lithium cells for many years. In most cases the power supply needs only minimal regulation.
The QT114 employs numerous signal acquisition and processing techniques pioneered by Quantum. No external switches, opamps, or other analog components aside from CS are required.
A unique feature is the 'slosh filter', a detection integrator which averages detections over a rolling 15 second interval before activating or deactivating the OUT pins. This filter allows use of the QT114 with violently moving fluids, for example in a moving vehicle, that would otherwise cause the outputs to flicker between two states.
The device also includes selectable output polarity, allowing both output lines to be made either active-high or active-low. It also includes the Quantum-pioneered HeartBeat™ signal, allowing a host controller to monitor the health of the QT114 continuously if desired. By using the charge transfer principle, the IC delivers a level of performance clearly superior to older technologies. It is specifically designed to replace electromechanical devices like float switches, thermistors, and conductance probes.
The QT114 is a digital burst mode charge-transfer (QT) sensor designed specifically for point level sensing; it includes all hardware and signal processing functions necessary to provide stable level sensing under a wide variety of changing conditions. Only a single external capacitor is required for operation.
Figure 1-1 shows a basic QT114 circuit using the device, with conventional OUT drives and power supply connections. The sensing electrode can be connected to a single-tier or 2-tier electrode as required.
Calibration is done by design, through adjustment of the electrode sizes and the Cs capacitor. Only under rare situations do QT114 circuits require calibration on an individual basis, and the circuit can make provision for that.
QT114 Data Sheet
