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PDF QT114 Data sheet ( Hoja de datos )
| Número de pieza | QT114 | |
| Descripción | CHARGE-TRANSFER QLEVEL SENSOR IC | |
| Fabricantes | QUANTUM | |
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Hay una vista previa y un enlace de descarga de QT114 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
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QProx™ QT114
CHARGE-TRANSFER QLEVEL™ SENSOR IC
! 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 outputs
Vcc
Out1
Out2
Filt
1
2
3
4
8 Gnd
7 Sns2
6 Sns1
5 Pol
APPLICATIONS -
! Process controls
! Vending machines
! Automotive fluids
! Consumer appliances
! Medical fluid sensing
! Soil moisture sensing
DESCRIPTION -
The QT114 QuickLevel™ charge-transfer (“QT”) sensor IC is specifically designed to detect point level in fluids
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.
TA
00C to +700C
-400C to +850C
Quantum Research Group Ltd
AVAILABLE OPTIONS
SOIC
QT114-S
QT114-IS
8-PIN DIP
QT114-D
-
Copyright © 1999 Quantum Research Group Ltd
R1.03
1 page  
Figure 2-8 Single Internal Horizontal Probe
T1
Figure 2-9 Twin-Level Internal Horizontal Probes
T2
Figure 2-10 Coaxial Probe For Non-Aqueous Fluids
Figure 2-11 Twin-Level Coaxial Probes For
Non-Aqueous Fluids
2.2.6 SCALE BUILDUP
Scale buildup on internal probes, bare or insulated, is not
generally a problem since the sensor is still measuring
capacitance, not conductance, and a reduction in
conductivity around the probe will have minimal or no effect.
Probe designs should be tested for this to be certain in all
specific cases.
A legitimate concern with bare metal probes is the buildup of
scale or other deposits at the entry point of the probe into the
vessel. Such deposits may create a conductive surface path
(especially if the vessel is made of metal) that may lead to
false-positive trips. If the shank of the probe at the entry
point is insulated enough so that conductive bridging cannot
occur, this problem should be alleviated.
2.2.7 VISCOUS, CONDUCTIVE FILMS
Highly viscous fluids, or those having a high surface tension,
and having substantial conductivity can fool some electrode
designs into thinking that there is fluid present when there is
not. This is a particular problem with external electrodes,
where the residual films of certain types of fluids inside the
container, electrically coupled to the fluid mass below, will
create a substantial capacitive response. Internal probes are
much more resistant to this effect since the fluid surface is
guaranteed to become mechanically disconnected from the
probe when the level drops. Coating the inner vessel surface
with a smooth plastic of polyethylene or PTFE often has a
very beneficial effect on this phenomenon.
2.3 SINGLE LEVEL SENSING
When sensing for a single trip point, the single electrode can
be a simple horizontal strip on the outside of a nonmetallic
vessel (Figure 2-2), or an internal probe having a substantial
horizontal 'plateau' at the trip point (Figures 2-4, 2-5, 2-8,
2-10). When the strip or plateau is ‘covered’ with fluid the IC
will detect on at least the OUT1 line; OUT2 can be ignored.
The trip point ideally occurs at the centerline of the internal
probe or external electrode; this can be trimmed with a
potentiometer if necessary (see Section 3.2). Making the
electrode narrow and long (horizontally) will help keep the
trip point localized within a narrow band.
-5-
5 Page 
4.5 DC SPECIFICATIONS
Vcc = 3.0V, Cs = 10nF, Cx = 10pF, TA = recommended range, unless otherwise noted
Parameter
Description
Min
Typ
Max
Units
Notes
VCC
IDD
VDDS
VIL
VHL
VOL
VOH
IIL
CX
S[1]
S[2]
Supply voltage
Supply current
Supply turn-on slope
Low input logic level
High input logic level
Low output voltage
High output voltage
Input leakage current
Load capacitance range
Sensitivity [T1]
Sensitivity [T2]
2.45
100
2.2
Vdd-0.8
0
20
0.125
0.33
5.25
0.8
0.6
±1
50
V
µA
V/s
V
V
V
V
µA
pF
pF/count
pF/count
Required for proper startup
FILT, POL
FILT, POL
OUT1, OUT2, 5mA sink
OUT1, OUT2, 1mA source
FILT, POL
Cs = 20nF, Cx = 10pF
Cs = 20nF, Cx = 30pF
FIGURE 4-1
FIGURE 4-2
Gain vs. Cx Load; Cs = 20nF; Vcc = 3.0
18
16
14
12
10
8
6
4
2
0
0.00
10.00
20.00
Cx Load, pF
30.00
40.00
Signal Level vs. Cx Load; Cs = 20nF; Vcc = 3.0
400
350
300
250
200
150
100
50
0
0.00
10.00
20.00
Cx Load, pF
30.00
40.00
4.6 PACKAGING
AVAILABLE TYPES:
DIP-8 0.26" / 6.5mm body, 0.100" pitch, plastic
SO8N 0.15" / 3.9mm body, 0.050" pitch, plastic
D suffix
S suffix
Refer to QT110 datasheet for complete dimensional information
4.7 CUSTOMIZATION
QT114 technology can be customized to suit specific requirement, often with little NRE charge or change in part cost.
Consult your rep or the factory for further information, or email to: [email protected]
- 11 -
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet QT114.PDF ] | |
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