The Original Gemini 88, item 780388, is no longer under support. However please find attached to this email the manual for those labs that still have a unit in good working condition. 

There are a couple of ways to determine if the pump is maintaining calibration.

Pusher Block Distance--Calibration check for syringe pumps:
 

Gravimetric Determination--Calibration check for syringe pumps:

It is recommended to use a Hamilton Glass Gastight syringe or other syringe (not plastic, which has an error of ±5%) that has little error (± 1%) 

Required:
Water
Syringe (Filled with a greater volume than that which you wish to dispense)
Balance
Weigh Boat
∗ Tare a weigh boat (or other liquid receptacle) on a balance
∗ Note the room temperature and determine the weight of the water based on the density of water at the temperature to which you are closest:

∗ Choose a syringe volume and set the pump to output a set volume at a set rate. Easiest: 1ml over 1 minute
∗ Time the dispense with a stopwatch (if desired), but the timer in the pump is virtually never a source of error
∗ Collect the dispensed water into the tared container and weigh the water. g/cm3 is equivalent to g/ml.
∗ If the density of water at ~20C (room temp) is .9982 g/ml, then .9982g is the goal weight of 1ml of the dispensed water that you wanted delivered in 1 minute (if you used suggested settings). The volume should be within ± 0.35% of the desired volume (0.5% if Pump11 Series). If it is off, it is probably due to syringe error:  Accuracy error is corrected by altering the set diameter of the syringe up or down on the pump in the same direction as the error (e.g. dispensed too much, increase set diameter so that the pusher block travels less distance)
∗ Repeat the dispense 10 times. Reproducibility should be within 0.1% 
∗ If your measurement does not fall within the reproducibility specifications then the pump has failed calibration check.