C-meter Sensitivity and Options
The sensitivity of the C-meter
is closely matched to that of the original British Mk5. With the sensitivity
booster set at 2 the range 1 to 32 corresponds closely to the physical scale
of the Mk5 rather than the numbering. The sensitivity control of the C-meter
has been arranged so that a given numeric increase in sensitivity will produce
the same percentage change in actual gain. The sensitivity booster positions
3 and 4 correspond to 64 and 128 on the Mk5. With the booster set at 1 and
the sensitivity at 1 a 360° scale corresponds to the full range of TA.
The following table shows the extra 3 options for gain available in the C-meter.
The sensitivity is modified according to the TA by being multiplied by factors
gain1, gain2, or gain3.
Calculations are based on a standard Wheatstone bridge with a 21250 ohm
bridge resistor using a voltage range from -1 to 1.
Column 1: Tone arm position.
Column 2: Corresponding resistance in ohms per the formula TA = PC/(PC
+ 21250)*5.55882353 + 0.94117647
Column 3: Voltage change in the bridge for a 1% resistance change.
Column 4: Additional gain needed to increase the sensitivity to make the
needle response equal for percentage changes in resistance independent of
TA.
Column 5: Voltage change using gain1.
Column 6: Additional gain needed to increase the sensitivity to make the
needle response equal for equal value changes in resistance independent
of TA.
Column 7: Voltage change using gain2.
Column 8: Modified gain to compensate for reduced sensitivity at low TA
using gain2. It selects the greater value of gain1 and gain2.
Column 9: Voltage change using gain3.
The factor used by the CofS Quantum appears based on an algorithm similar
to gain2.
TA
|
Resistance
|
dV
|
gain1
|
AdV1
|
gain2
|
AdV2
|
gain3
|
AdV3
|
| 1.0 |
227 |
0.0002 |
23.88 |
0.0050 |
0.05 |
0.0000 |
23.88 |
0.0050 |
| 1.1 |
625 |
0.0006 |
9.01 |
0.0050 |
0.13 |
0.0001 |
9.01 |
0.0050 |
| 1.2 |
1038 |
0.0009 |
5.63 |
0.0050 |
0.21 |
0.0002 |
5.63 |
0.0050 |
| 1.3 |
1466 |
0.0012 |
4.14 |
0.0050 |
0.29 |
0.0004 |
4.14 |
0.0050 |
| 1.4 |
1912 |
0.0015 |
3.30 |
0.0050 |
0.38 |
0.0006 |
3.30 |
0.0050 |
| 1.5 |
2375 |
0.0018 |
2.76 |
0.0050 |
0.48 |
0.0009 |
2.76 |
0.0050 |
| 1.6 |
2857 |
0.0021 |
2.39 |
0.0050 |
0.57 |
0.0012 |
2.39 |
0.0050 |
| 1.7 |
3359 |
0.0024 |
2.12 |
0.0050 |
0.67 |
0.0016 |
2.12 |
0.0050 |
| 1.8 |
3883 |
0.0026 |
1.91 |
0.0050 |
0.78 |
0.0020 |
1.91 |
0.0050 |
| 1.9 |
4429 |
0.0028 |
1.75 |
0.0050 |
0.89 |
0.0025 |
1.75 |
0.0050 |
| 2.0 |
5000 |
0.0031 |
1.62 |
0.0050 |
1.00 |
0.0031 |
1.62 |
0.0050 |
| 2.1 |
5597 |
0.0033 |
1.52 |
0.0050 |
1.12 |
0.0037 |
1.52 |
0.0050 |
| 2.2 |
6221 |
0.0035 |
1.43 |
0.0050 |
1.24 |
0.0043 |
1.43 |
0.0050 |
| 2.3 |
6875 |
0.0037 |
1.35 |
0.0050 |
1.38 |
0.0051 |
1.38 |
0.0051 |
| 2.4 |
7561 |
0.0039 |
1.29 |
0.0050 |
1.51 |
0.0058 |
1.51 |
0.0058 |
| 2.5 |
8281 |
0.0040 |
1.24 |
0.0050 |
1.66 |
0.0067 |
1.66 |
0.0067 |
| 2.6 |
9038 |
0.0042 |
1.19 |
0.0050 |
1.81 |
0.0075 |
1.81 |
0.0075 |
| 2.7 |
9836 |
0.0043 |
1.16 |
0.0050 |
1.97 |
0.0085 |
1.97 |
0.0085 |
| 2.8 |
10676 |
0.0044 |
1.12 |
0.0050 |
2.14 |
0.0095 |
2.14 |
0.0095 |
| 2.9 |
11563 |
0.0045 |
1.10 |
0.0050 |
2.31 |
0.0105 |
2.31 |
0.0105 |
| 3.0 |
12500 |
0.0046 |
1.07 |
0.0050 |
2.50 |
0.0116 |
2.50 |
0.0116 |
| 3.1 |
13493 |
0.0047 |
1.05 |
0.0050 |
2.70 |
0.0128 |
2.70 |
0.0128 |
| 3.2 |
14545 |
0.0048 |
1.04 |
0.0050 |
2.91 |
0.0140 |
2.91 |
0.0140 |
| 3.3 |
15664 |
0.0049 |
1.02 |
0.0050 |
3.13 |
0.0152 |
3.13 |
0.0152 |
| 3.4 |
16855 |
0.0049 |
1.01 |
0.0050 |
3.37 |
0.0166 |
3.37 |
0.0166 |
| 3.5 |
18125 |
0.0049 |
1.01 |
0.0050 |
3.63 |
0.0179 |
3.63 |
0.0179 |
| 3.6 |
19483 |
0.0050 |
1.00 |
0.0050 |
3.90 |
0.0194 |
3.90 |
0.0194 |
| 3.7 |
20938 |
0.0050 |
1.00 |
0.0050 |
4.19 |
0.0208 |
4.19 |
0.0208 |
| 3.8 |
22500 |
0.0050 |
1.00 |
0.0050 |
4.50 |
0.0224 |
4.50 |
0.0224 |
| 3.9 |
24183 |
0.0050 |
1.00 |
0.0050 |
4.84 |
0.0240 |
4.84 |
0.0240 |
| 4.0 |
26000 |
0.0049 |
1.01 |
0.0050 |
5.20 |
0.0256 |
5.20 |
0.0256 |
| 4.1 |
27969 |
0.0049 |
1.02 |
0.0050 |
5.59 |
0.0273 |
5.59 |
0.0273 |
| 4.2 |
30109 |
0.0048 |
1.03 |
0.0050 |
6.02 |
0.0290 |
6.02 |
0.0290 |
| 4.3 |
32443 |
0.0048 |
1.05 |
0.0050 |
6.49 |
0.0308 |
6.49 |
0.0308 |
| 4.4 |
35000 |
0.0047 |
1.06 |
0.0050 |
7.00 |
0.0327 |
7.00 |
0.0327 |
| 4.5 |
37813 |
0.0046 |
1.09 |
0.0050 |
7.56 |
0.0346 |
7.56 |
0.0346 |
| 4.6 |
40921 |
0.0045 |
1.11 |
0.0050 |
8.18 |
0.0366 |
8.18 |
0.0366 |
| 4.7 |
44375 |
0.0043 |
1.14 |
0.0050 |
8.88 |
0.0386 |
8.88 |
0.0386 |
| 4.8 |
48235 |
0.0042 |
1.18 |
0.0050 |
9.65 |
0.0407 |
9.65 |
0.0407 |
| 4.9 |
52578 |
0.0041 |
1.22 |
0.0050 |
10.52 |
0.0428 |
10.52 |
0.0428 |
| 5.0 |
57500 |
0.0039 |
1.27 |
0.0050 |
11.50 |
0.0450 |
11.50 |
0.0450 |
| 5.1 |
63125 |
0.0037 |
1.33 |
0.0050 |
12.63 |
0.0472 |
12.63 |
0.0472 |
| 5.2 |
69615 |
0.0036 |
1.40 |
0.0050 |
13.92 |
0.0495 |
13.92 |
0.0495 |
| 5.3 |
77188 |
0.0034 |
1.48 |
0.0050 |
15.44 |
0.0519 |
15.44 |
0.0519 |
| 5.4 |
86136 |
0.0031 |
1.58 |
0.0050 |
17.23 |
0.0543 |
17.23 |
0.0543 |
| 5.5 |
96875 |
0.0029 |
1.69 |
0.0050 |
19.38 |
0.0567 |
19.38 |
0.0567 |
| 5.6 |
110000 |
0.0027 |
1.84 |
0.0050 |
22.00 |
0.0592 |
22.00 |
0.0592 |
| 5.7 |
126406 |
0.0024 |
2.03 |
0.0050 |
25.28 |
0.0618 |
25.28 |
0.0618 |
| 5.8 |
147500 |
0.0022 |
2.27 |
0.0050 |
29.50 |
0.0644 |
29.50 |
0.0644 |
| 5.9 |
175625 |
0.0019 |
2.60 |
0.0050 |
32.00 |
0.0611 |
32.00 |
0.0611 |
| 6.0 |
215000 |
0.0016 |
3.05 |
0.0050 |
32.00 |
0.0519 |
32.00 |
0.0519 |
| 6.1 |
274063 |
0.0013 |
3.74 |
0.0050 |
32.00 |
0.0423 |
32.00 |
0.0423 |
| 6.2 |
372500 |
0.0010 |
4.90 |
0.0050 |
32.00 |
0.0324 |
32.00 |
0.0324 |
| 6.3 |
569375 |
0.0007 |
7.21 |
0.0050 |
32.00 |
0.0220 |
32.00 |
0.0220 |
| 6.4 |
1160000 |
0.0003 |
14.15 |
0.0050 |
32.00 |
0.0112 |
32.00 |
0.0112 |