SECTION 1 - RGH20 direct output readheads
(continued)
Electrical connections
RGH20 grounding and shielding
RGH20
Inner shield
Outer shield
Extension cable*
Out put
signals
5 V
0 V
Customer
electronics
*Maximum extension cable length:
RGH20B - 100 m, RGH20D, X, Z - 50 m RGH20W, Y, H, I, O - 20 m
IMPORTANT:
The outer shield should be connected to the machine earth (Field Ground).
The inner shield should be connected to 0 V. Care should be taken to ensure that the inner and outer
shields are insulated from each other. If the inner and outer shields are connected together, this will
cause a short between 0 V and earth, which could cause electrical noise issues.
Recommended signal termination
Digital outputs RGH20D, X, Z, W, Y, H, I, O
Standard RS422A line receiver circuitry.
Contact Renishaw for further details on receiver termination for 3-state output.
Analogue output - type RGH20B
V
q
V
0
V
1
V
2
+
V
q
V
0
V
1
V
2
-
120R
Readhead
A B Z E Q+
Cable Z
0
= 120R
Customer electronics
120R
A B Z E Q-
Speed
Digital readheads
The tables below show the max i mum speed and as so ci at ed minimum rec eiver
clock frequency for all dig it al output readheads.
Analogue readhead
(1Vpp) RGH20B
Signal amplitude (%)
500
10
100
10
1
100
2
4
6
m/s
50
70
Frequency (kHz)
The RGH20Y, RGH20W, RGH20H, RGH20I and RGH20O digital output readheads
have clocked outputs. These are designed to prevent fi ne edge sep a ra tions being
missed by receiving elec tron ics uti lis ing slower clock speeds.
Head type
RGH20D (5 µm)
RGH20X (1 µm)
RGH20Z (0.5 µm)
Minimum receiver clock frequency
(MHz)
encoder velocity (m/s)
resolution (µm)
x 4 safety factor
)
)
Maximum
speed (m/s)
8
5
3
Option code
Head type
30
31
32
33
Minimum
receiver clock
frequency
(MHz)
12
8
6
4
Maximum speed (mm/s)
RGH20O
(10 nm)
65
45
–
20
RGH20I
(20 nm)
130
90
–
40
RGH20H
(50 nm)
350
250
–
120
RGH20Y
(0.1 µm)
700
500
–
250
RGH20W
(0.2 µm)
–
–
700
500