Hello,
I'm trying to use the LDC1000 to measure the change of inductance in a RIP-Belt (belt with a woven wire) and encountered some difficulties.
1. The d/s states "Conversion data is updated to these registers only when a read is initiated on 0x21 register." while in fact it seems 0x20 (Status) has the described effect?
2. DRDYB Mode: INTB is supposed to be pulsed when a read is in progress. However figure 20 shows that it is held high instead, which is also what I abserve when scoping the line....?
3. SPI write commands: "Data is written into the register on the rising edge of the 16th clock." - That does not seem to be the case either. I always have to send another Byte (or generate additional clock flanks) for the value to be written (while keeping CSB set, of course) - no matter the polarity or phase of the SPI clock on the MSP430F5659 side...?
4. Regarding the L-resolution, I currently only get like 4-Bit of resolution for my setup no matter what settings i choose for the resgisters / filter capacitor (was told here to change from 100pF to 33pF to increase resolution). Here are some example configurations (last column values are way out of range but were suggested here):
Setting | Value | Register | Setting | Value | Register | Setting | Value | Register |
C_F (pF) | 100 | C_F (pF) | 33 | C_F (pF) | 10 | |||
C_TANK (pF) | 470 | C_TANK (pF) | 470 | C_TANK (pF) | 66 | |||
Fmin (Hz) | 500000 | 159 | Fmin (Hz) | 4000000 | 221 | Fmin (Hz) | 500000 | 159 |
Ampl (V) | 4 | 10 | Ampl (V) | 2 | 1 | Ampl (V) | 2 | 1 |
RT | 6144 | 111 | RT | 6144 | 111 | RT | 6144 | 111 |
Rp_Max | 1347 | 0x1D | Rp_Max | 1347 | 0x1D | Rp_Max | 1796 | 0x1C |
Rp_Min | 1026 | 0x3E | Rp_Min | 1026 | 0x3E | Rp_Min | 1347 | 0x1D |
FREQ | (max) | 4043 | FREQ | (max) | 4011 | FREQ | (max) | 1815 |
(min) | 3991 | (min) | 3961 | (min) | 1794 | |||
(diff.) | 52 | (diff.) | 50 | (diff.) | 21 | |||
PROX | 15500 | PROX | 13870 | PROX | 21000 | |||
12250 | 10900 | 18600 | ||||||
3250 | 2970 | 2400 | ||||||
Y | 0.4730 | Y | 0.4233 | Y | 0.6409 | |||
0.3738 | 0.3326 | 0.5676 | ||||||
Rp (Ohm) | 1173.35 | Rp (Ohm) | 1189.48 | Rp (Ohm) | 1479.87 | |||
1205.95 | 1220.03 | 1510.25 | ||||||
F_sensor (Hz) | 4052436.31 | F_sensor (Hz) | 4084766.89 | F_sensor (Hz) | 9026997.25 | |||
4105236.78 | 4136329.21 | 9132664.44 | ||||||
L (uH) | 3.28 | L (uH) | 3.23 | L (uH) | 4.71 | |||
3.20 | 3.15 | 4.60 |
So what can i do to get more than 4-Bit resolution out of the 24-Bit stated in the prodcut description?
PS: When measuring the inductance of the belt externally I get ~4uH (at 1 Hz - 100kHz).