Metrohm 765 Dosimat - Manual (Page 61)

5.5 Continuous dosing with two Dosimats
765 Dosimat
57
5.5 Continuous dosing with two Dosimats
Two 765 Dosimats are suitable for continuous dosing.
The two 765 Dosimats are connected with cable 3.980.3140 via both interfaces RS232 (6).
Procedure
• Select mode DIS C in both Dosimats.
• Set on both Dosimats the dispensing volume equal to the volume of the mounted
exchange unit (V-DIS = V
burette
).
If one of the Dosimats is started and reaches the preselected dispensing volume, this
triggers the start of the other Dosimat, etc.
• Prerequisite for continuous dosing is that the filling rate is higher than the expelling rate
(while one Dosimat is expelling, the other one is refilling i.e. in addition to the
movement of the piston two turns of the cock are necessary, about 2 s for each
turning).
Example: rate ↑ ≤ 0.85 rate ↓
max
for the smaller of the exchange unit
At high rates, the effective expelling rate can deviate from the set rate by max. 4 % as a
result of the finite resolution of the digital rate control, but the effective rate is held
constant with quartz crystal accuracy.
If dosing to a fixed end volume V is envisaged, V-LIM is set according to the following
rules:
• Calculation of the number of complete cycles N (V
1
and V
2
be completely expelled):
V
N = INT ———— (integral quotient)
V
1
+ V
2
• Calculation of the remaining volume V
R
:
V
R
= V - N
*
(V
1
+ V
2
)
• In case the remaining volume is V
R
=0, Dosimat 2 is the final burette.
Settings on Dosimat 1:
V-LIM(1) = OFF
VDIS(1) = V
1
Settings on Dosimat 2:
V-LIM(2) = N
*
V
2
V-DIS(2) = V
2
• In case the remaining volume is V
R
≠0 and V
R
≤ V
1
, Dosimat 1 is the final burette.
Settings on Dosimat 1:
V-LIM(1) = V - N * V
2
VDIS(1) = V
1
Settings on Dosimat 2:
V-LIM(2) = OFF
V-DIS(2) = V
2
• In case the remaining volume is V
R
≠0 and V
R
> V
1
, Dosimat 2 is the final burette.
Settings on Dosimat 1:
V-LIM(1) = OFF
VDIS(1) = V
1
Settings on Dosimat 2:
V-LIM(2) = V - V
1
* (N + 1)
V-DIS(2) = V
2
with
V
1
cylinder volume on Dosimat 1 (start Dosimat)
V
2
cylinder volume on Dosimat 2