Seiko Instruments LTP F Series - Manual (Page 42)

3-24
3.6.3 Adjustment of the Head Resistance
Adjustment of the head resistance is according to equation (4). Due to wiring resistance there is a
drop in voltage.
Equation (4):
R=
RH:Head resistance, RH=650 Ω
Ri: Wiring resistance in the thermal head ( Ω), Ri=25Ω
R
C
: Common terminal wiring resistance in the thermal head
LTPF247 R
C
=0.14 ( Ω)
LTPF347 R
C
=0.165 ( Ω)
r
c
: Wiring resistance between Vp and GND ( Ω) ∗1
N: Number of dots driven at the same time
∗1
This resistance value is equal to the resistance of the wire used between the thermal head control connector and the
power supply including the resistance of switching circuit of relay, etc.
3.6.4 Head Activation Pulse Term Coefficient
According to equation (5), calculate the compensation coefficient of the head activation pulse term
(equal motor drive frequency) to get the constant printing density even when changing the printing
speed such as start up acceleration control.
Equation (5):
C=2.7 -
Cx: Speed correction coefficient 1.57
W: Head activation cycle of one dot line (ms)
∗ When the motor drive frequency is 666 pps or less:
W = 666 pps (fixed)
RH
( RH + Ri + (Rc + rc )
×
N ) 2
3.59
Cx + W