MIDGARDThe third generation of the popular precision current source, designed at M.I.T. for the iontophoresis of neural transport tracers such as horseradish peroxidase (HRP) or tritiated amino acids into neural tissue, is now manufactured by Stoelting. It may also be used to make small lesions ; and in applications requiring precise current control through high impedance. The instrument is easy to use and reliable.
2000V Compliance voltage
The new Midgard features a higher compliance voltage (2000V) for injections from very small or partially clogged pipette tips. The output current level can be regulated to +/- 0.5% from 0.0 to 200Megohms.
Pulsed or Continuous Output
Pulpsed output helps avoid clogging or polarization of the tip of the pipette. The user may select pulsed or continuous current with a switch. The pulsed on/off times are factory set to 7 sec. on/7 sec. off, but can be separately controlled on an internal pot.
Many users have requested external timing control for lab automation applications. The new Midgard can be gated through a BNC jack on the rear panel by any laboratory logic pulse generator. The output current is continuous whenever the gating jack is logic high, off when it is logic low.
A special switch allows reversing polarity. This is useful when using a retaining current to hold the pipette contents in during approach. Two high voltage cables, a 200Megohm test resistor and user’s manual are included with each Precision Current Source.
|Output Current||0 - 20 µA, set by ten-turn dial|
|Load Current Accuracy||0.5%, 1 Megohm - 200 Megohm|
|Load Current epeatability||0.25%|
|Polarity||+/-, switch selected|
|Load Configuration||Load must be floating|
|Display Resolution||0.01 µA|
|Output Connectors||Two binding posts|
PULSED MODE OPERATION
|Pulse Duration||7 seconds, preset|
|Duty Cycle||50% (7 on/ 7 off)|
|Timing Error||1% typical|
|Timing Error Drift||0.50% 1ºC|
|Load Current Fall Time||0.1 sec|
|Load Current Rise Time||Dependent on load resistance.
For 7.0 µA through 200 Megohms,rise time to 99% of set value is 1 sec;
overshoot less than 5%